System and method for determining engine knock

ABSTRACT

Systems and methods for detecting and controlling knock in an engine are presented. In one example, engine knock sensors are selected based on whether or not certain cylinders are activated and combusting air and fuel or deactivated and not combusting air and fuel. Output of selected knock sensors is the basis for adjusting engine spark timing.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 62/347,875, filed on Jun. 9, 2016. The entirecontents of the above-referenced application are hereby incorporated byreference in its entirety for all purposes.

FIELD

The present description relates to systems and methods for controllingengine knock of an engine. The systems and methods may be applied toengines that may deactivate selected engine cylinders via poppet valves.

BACKGROUND AND SUMMARY

An engine may include one or more knock sensors to sense engine knock.In a petrol engine, knock occurs in an engine after an air-fuel mixturein the cylinder is ignited by a spark. In particular, the air-fuelmixture is ignited at a location in the cylinder outside of a flamefront in the cylinder created by the spark. The second ignition afterthe spark ignition is produced by rising pressure in the cylinder and itcauses a pressure oscillation in the cylinder that produces a ping orknocking sound in the engine. The engine block may include severalcylinders and support structures that may improve or degrade thecapacity of the engine knock sensors to detect engine knock.Consequently, two or more knock sensors may be deployed in an engine todetect engine knock. However, it may be difficult to detect engine knockwith even two engine knock sensors since combustion noise and vibrationof the engine block may mask engine knock that is detectable via theengine knock sensors.

The inventors herein have recognized the above-mentioned disadvantagesand have developed a method for operating an engine, comprising:operating the engine with a first group of combusting cylinders inresponse to a first condition; operating the engine with a second groupof combusting cylinders in response to a second condition; adjustingspark timing of a cylinder in response to an indication of knock via afirst group of sensors during the first condition; and adjusting sparktiming of the cylinder in response to an indication of knock via asecond group of sensors during the second condition.

By adjusting spark timing in response to different groups of knocksensors during different engine operating conditions, it may be possibleto provide the technical result of improved engine knock detection. Forexample, if all engine cylinders are active and combusting air and fuel,it may be desirable to assess the presence or absence of engine knockvia two engine knock sensors. However, if one or more cylinders isdeactivated and not combusting air and fuel, it may be desirable toassess the presence or absence of engine knock via a single sensor andignore output of a second sensor. Deactivating one or more enginecylinders may reduce combustion noise and improve a signal to noiseratio of a knock sensor.

The present description may provide several advantages. In particular,the approach may improve engine knock sensing. Additionally, theapproach may reduce the possibility of engine degradation. Further, theapproach may improve engine knock sensing when cylinders of an engineare deactivated in different ways.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingan example of an embodiment, referred to herein as the DetailedDescription, when taken alone or with reference to the drawings, where:

FIG. 1A is a schematic diagram of a single cylinder of an engine;

FIG. 1B is a schematic diagram of the engine of FIG. 1A included in apowertrain;

FIGS. 2A-2F show example valve configurations for four cylinder engineswith cylinders that may be deactivated;

FIGS. 3A and 3B show example patterns of activated and deactivatedcylinders of a four cylinder engine;

FIGS. 4A-4C show example valve configurations for eight cylinder enginewith cylinders that may be deactivated;

FIG. 5A shows example camshafts for a hydraulically operated valvedeactivating system;

FIG. 5B shows example deactivating valve operators for the hydraulicallyoperated valve deactivating system shown in FIG. 5A;

FIG. 5C shows an example valve operator for the hydraulically operatedvalve deactivating system shown in FIG. 5A;

FIG. 5D shows an example cylinder and valve deactivation sequence forthe hydraulically operated valve deactivating system shown in FIG. 5A;

FIG. 6A shows an example camshaft for an alternative hydraulicallyoperated valve deactivating system;

FIG. 6B shows a cross section of a camshaft and saddle for thehydraulically operated valve deactivating system shown in FIG. 6A;

FIG. 6C shows example valve deactivating valve operators for thehydraulically operated valve deactivating system shown in FIG. 6A;

FIG. 6D is an example cylinder and valve deactivation sequence for thehydraulically operated valve deactivating system shown in FIG. 6A;

FIG. 7 is a flowchart of an example method for operating an engine withdeactivating cylinders and valves;

FIG. 8A is a flowchart of an example method for selectively activatingand deactivating cylinders and cylinder valves of an engine with bothdeactivating and non-deactivating intake valves and onlynon-deactivating exhaust valves;

FIG. 8B is a block diagram for estimating an amount of oil in adeactivated cylinder;

FIG. 9 is an example sequence for activating and deactivating cylindersand cylinder valves of an engine having both deactivating andnon-deactivating intake valves and only non-deactivating exhaust valves;

FIG. 10 is a flowchart of an example method for selectively activatingand deactivating cylinders and cylinder valves of an engine with bothdeactivating and non-deactivating intake valves and non-deactivating anddeactivating exhaust valves;

FIG. 11 is a flowchart of a method for determining available cylindermodes;

FIG. 12 is a flowchart of a method for evaluating whether or notcylinder deactivation may be performed responsive to cylinderactivation/deactivation busyness;

FIG. 13 is a sequence showing cylinder activation and deactivationaccording to the method of FIG. 12;

FIG. 14 is a flowchart of a method for evaluating engine fuelconsumption as a basis for selectively allowing cylinder deactivation;

FIG. 15 is a flowchart of a method for evaluating engine fuelconsumption as a basis for selectively allowing cylinder deactivation;

FIG. 16 is a flowchart of a method for evaluating engine cam phasing forselecting engine cylinder modes;

FIG. 17 is a sequence showing selecting engine cylinder modes responsiveto engine cam phasing;

FIG. 18 is a flowchart of a method for selecting engine cylinder moderesponsive to engine fuel consumption based on operating an engine invarious transmission gears;

FIG. 19 is a sequence showing selecting transmission gears and an actualtotal number of active cylinders to improve engine fuel consumption;

FIG. 20 is a flowchart of a method for selecting different enginecylinder modes in while operating a vehicle in various decelerationmodes;

FIG. 21 is a sequence for operating an engine in different cylindermodes based on operating a vehicle in different deceleration modes;

FIG. 22 is a flowchart for determining if conditions are present foroperating an engine in various variable displacement (VDE) engine modes;

FIG. 23 is a flowchart of a method for controlling engine intakemanifold pressure;

FIG. 24 is a sequence showing engine intake manifold pressure controlaccording to the method of FIG. 23;

FIG. 25 is a flowchart of a method for controlling engine intakemanifold pressure;

FIG. 26 is an operating sequence for controlling engine intake manifoldpressure;

FIGS. 27A and 27B show a flowchart for adjusting engine actuators toimprove engine cylinder mode changes;

FIGS. 28A and 28B show sequences for improving cylinder mode changes;

FIG. 29 is a flowchart for delivering fuel to an engine during cylindermode changes;

FIG. 30 is a sequence for showing fuel delivery to an engine duringcylinder mode changes;

FIG. 31 is a flowchart of a method for controlling engine oil pressureduring cylinder mode changes;

FIG. 32 is a sequence showing oil pressure control during cylinder modechanges;

FIG. 33 is a flowchart of a method to improve engine knock controlduring cylinder mode changes;

FIG. 34 is a sequence showing engine knock control during differentengine cylinder modes;

FIG. 35 is a flowchart of a method for adjusting spark gain;

FIG. 36 is a sequence showing adjustable spark gain;

FIG. 37 is a flowchart of a method for determining a knock referencevalue depending on cylinder mode;

FIG. 38 is a sequence showing selection of a knock reference value;

FIG. 39 is a flowchart of a method for selecting engine cylinder modesin the presence of valve degradation;

FIG. 40 is a flowchart of a sequence for selecting engine cylinder modesin the presence of valve degradation;

FIG. 41 is a flowchart for sampling an oxygen sensor responsive tocylinder deactivation; and

FIG. 42 is a flowchart for sampling a camshaft sensor responsive tocylinder deactivation.

DETAILED DESCRIPTION

The present description is related to systems and methods forselectively activating and deactivating cylinders and cylinder valves ofan internal combustion engine. The engine may be configured and operateas is shown in FIGS. 1A-6D. Various methods and prophetic operatingsequences for an engine that includes deactivating valves are shown inFIGS. 7-42. The different methods may operate cooperatively and with thesystems shown in FIGS. 1A-6D.

Referring to FIG. 1A, internal combustion engine 10, comprising aplurality of cylinders, one cylinder of which is shown in FIG. 1A, iscontrolled by electronic engine controller 12. Engine 10 is comprised ofcylinder head casting 35 and block 33, which include combustion chamber30 and cylinder walls 32. Piston 36 is positioned therein andreciprocates via a connection to crankshaft 40. Flywheel 97 and ringgear 99 are coupled to crankshaft 40. Starter 96 (e.g., low voltage(operated with less than 30 volts) electric machine) includes pinionshaft 98 and pinion gear 95. Pinion shaft 98 may selectively advancepinion gear 95 to engage ring gear 99. Starter 96 may be directlymounted to the front of the engine or the rear of the engine. In someexamples, starter 96 may selectively supply torque to crankshaft 40 viaa belt or chain. In one example, starter 96 is in a base state when notengaged to the engine crankshaft.

Combustion chamber 30 is shown communicating with intake manifold 44 andexhaust manifold 48 via respective intake valve 52 and exhaust valve 54.Each intake and exhaust valve may be operated by an intake camshaft 51and an exhaust camshaft 53. The position of intake camshaft 51 may bedetermined by intake cam sensor 55. The position of exhaust camshaft 53may be determined by exhaust cam sensor 57. An angular position ofintake valve 52 may be moved relative to crankshaft 40 via phasingadjusting device 59. An angular position of exhaust valve 54 may bemoved relative to crankshaft 40 via phasing adjusting device 58. Valveoperators shown in detail below may transfer mechanical energy fromintake camshaft 51 to intake valve 52 and from exhaust camshaft 53 toexhaust valve 54. Further, in other examples, a single camshaft mayoperate intake valve 52 and exhaust valve 54.

Fuel injector 66 is shown positioned to inject fuel directly intocylinder 30, which is known to those skilled in the art as directinjection. Optional fuel injector 67 is shown positioned to port injectfuel to cylinder 30, which is known to those skilled in the art as portfuel injection. Fuel injectors 66 and 67 deliver liquid fuel inproportion to pulse widths from controller 12. Fuel is delivered to fuelinjectors 66 and 67 by a fuel system (not shown) including a fuel tank,fuel pump, and fuel rail (not shown). In one example, a high pressure,dual stage, fuel system may be used to generate higher fuel pressures.

In addition, intake manifold 44 is shown communicating with turbochargercompressor 162 and engine air intake 42. In other examples, compressor162 may be a supercharger compressor. Shaft 161 mechanically couplesturbocharger turbine 164 to turbocharger compressor 162. Optionalelectronic throttle or central throttle 62 adjusts a position ofthrottle plate 64 to control air flow from compressor 162 to intakemanifold 44. Pressure in boost chamber 45 may be referred to a throttleinlet pressure since the inlet of throttle 62 is within boost chamber45. The throttle outlet is in intake manifold 44. In some examples, acharge motion control valve 63 is positioned downstream of throttle 62and upstream of intake valve 52 in a direction of air flow into engine10 and operated by controller 12 to regulate air flow into combustionchamber 30. Compressor recirculation valve 47 may be selectivelyadjusted to a plurality of positions between fully open and fullyclosed. Waste gate 163 may be adjusted via controller 12 to allowexhaust gases to selectively bypass turbine 164 to control the speed ofcompressor 162. Air filter 43 cleans air entering engine air intake 42.

Distributorless ignition system 88 provides an ignition spark tocombustion chamber 30 via spark plug 92 in response to controller 12.Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled toexhaust manifold 48 upstream of catalytic converter 70. Alternatively, atwo-state exhaust gas oxygen sensor may be substituted for UEGO sensor126. Pressure sensor 127 is shown positioned in exhaust manifold 48 asan exhaust pressure sensor. Alternatively, pressure sensor 127 may beposition in combustion chamber 30 as a cylinder pressure sensor. Sparkplug 92 may also serve as an ion sensor for ignition system 88.

Converter 70 can include multiple catalyst bricks, in one example. Inanother example, multiple emission control devices, each with multiplebricks, can be used. Converter 70 can be a three-way type catalyst inone example. Further, converter 70 may include a particulate filter.

Controller 12 is shown in FIG. 1A as a conventional microcomputerincluding: microprocessor unit 102, input/output ports 104, read-onlymemory 106 (e.g., non-transitory memory), random access memory 108, keepalive memory 110, and a conventional data bus. Controller 12 is shownreceiving various signals from sensors coupled to engine 10, in additionto those signals previously discussed, including: engine coolanttemperature (ECT) from temperature sensor 112 coupled to cooling sleeve114; engine mount with integrated vibration and/or movement sensors 117which may provide feedback to compensate and evaluate engine noise,vibration, and harshness; a position sensor 134 coupled to anaccelerator pedal 130 for sensing force applied by foot 132; a positionsensor 154 coupled to brake pedal 150 for sensing force applied by foot152, a measurement of engine manifold pressure (MAP) from pressuresensor 122 coupled to intake manifold 44; an engine position sensor froma Hall effect sensor 118 sensing crankshaft 40 position; a measurementof air mass entering the engine from sensor 120; and a measurement ofthrottle position from sensor 68. Barometric pressure may also be sensed(sensor not shown) for processing by controller 12. In a preferredaspect of the present description, engine position sensor 118 produces apredetermined number of equally spaced pulses every revolution of thecrankshaft from which engine speed (RPM) can be determined. Controller12 may also receive information from other sensors 24 which may includebut are not limited to engine oil pressure sensors, ambient pressuresensors, and engine oil temperature sensors.

During operation, each cylinder within engine 10 typically undergoes afour stroke cycle: the cycle includes the intake stroke, compressionstroke, expansion stroke, and exhaust stroke. A cylinder cycle for afour stroke engine is two engine revolutions and an engine cycle is alsotwo revolutions. During the intake stroke, generally, the exhaust valve54 closes and intake valve 52 opens. Air is introduced into combustionchamber 30 via intake manifold 44, and piston 36 moves to the bottom ofthe cylinder so as to increase the volume within combustion chamber 30.The position at which piston 36 is near the bottom of the cylinder andat the end of its stroke (e.g. when combustion chamber 30 is at itslargest volume) is typically referred to by those of skill in the art asbottom dead center (BDC).

During the compression stroke, intake valve 52 and exhaust valve 54 areclosed. Piston 36 moves toward the cylinder head casting 35 so as tocompress the air within combustion chamber 30. The point at which piston36 is at the end of its stroke and closest to the cylinder head casting35 (e.g. when combustion chamber 30 is at its smallest volume) istypically referred to by those of skill in the art as top dead center(TDC). In a process hereinafter referred to as injection, fuel isintroduced into the combustion chamber. In a process hereinafterreferred to as ignition, the injected fuel is ignited by known ignitionmeans such as spark plug 92, resulting in combustion.

During the expansion stroke, the expanding gases push piston 36 back toBDC. Crankshaft 40 converts piston movement into a rotational torque ofthe rotary shaft. Finally, during the exhaust stroke, the exhaust valve54 opens to release the combusted air-fuel mixture to exhaust manifold48 and the piston returns to TDC. Note that the above is shown merely asan example, and that intake and exhaust valve opening and/or closingtimings may vary, such as to provide positive or negative valve overlap,late intake valve closing, or various other examples.

Driver demand torque may be determined via a position of acceleratorpedal 130 and vehicle speed. For example, accelerator pedal position andvehicle speed may index a table that outputs a driver demand torque. Thedriver demand torque may represent a desired engine torque or torque ata location along a driveline that includes the engine. Engine torque maybe determined from driver demand torque via adjusting the driver demandtorque for gear ratios, axle ratios, and other driveline components.

Referring now to FIG. 1B, FIG. 1B is a block diagram of a vehicle 125including a driveline 100. The driveline of FIG. 1B includes engine 10shown in FIG. 1A. Driveline 100 may be powered by engine 10. Enginetorque may be adjusted via engine torque actuator 191, which may be afuel injector, camshaft, throttle, or other device. Engine crankshaft 40is shown coupled to torque converter 156. In particular, enginecrankshaft 40 is mechanically coupled to torque converter impeller 285.Torque sensor 41 provides torque feedback and it may be used to evaluateengine noise, vibration, and harshness. Torque converter 156 alsoincludes a turbine 186 to output torque to transmission input shaft 170.Transmission input shaft 170 mechanically couples torque converter 156to automatic transmission 158. Torque converter 156 also includes atorque converter bypass lock-up clutch 121 (TCC). Torque is directlytransferred from impeller 185 to turbine 186 when TCC is locked. TCC iselectrically operated by controller 12. Alternatively, TCC may behydraulically locked. In one example, the torque converter may bereferred to as a component of the transmission.

When torque converter lock-up clutch 121 is fully disengaged, torqueconverter 156 transmits engine torque to automatic transmission 158 viafluid transfer between the torque converter turbine 186 and torqueconverter impeller 185, thereby enabling torque multiplication. Incontrast, when torque converter lock-up clutch 121 is fully engaged, theengine output torque is directly transferred via the torque converterclutch to an input shaft 170 of transmission 158. Alternatively, thetorque converter lock-up clutch 121 may be partially engaged, therebyenabling the amount of torque directly relayed to the transmission to beadjusted. The controller 12 may be configured to adjust the amount oftorque transmitted by torque converter 121 by adjusting the torqueconverter lock-up clutch in response to various engine operatingconditions, or based on a driver-based engine operation request.

Automatic transmission 158 includes gears (e.g., reverse and gears 1-6)136 and forward clutches 135 for the gears. The gears 136 (e.g., 1-10)and clutches 135 may be selectively engaged to propel a vehicle. Torqueoutput from the automatic transmission 158 may in turn be relayed towheels 116 to propel the vehicle via output shaft 160. Specifically,automatic transmission 158 may transfer an input driving torque at theinput shaft 170 responsive to a vehicle traveling condition beforetransmitting an output driving torque to the wheels 116.

Further, a frictional force may be applied to wheels 116 by engagingwheel brakes 119. In one example, wheel brakes 119 may be engaged inresponse to the driver pressing his foot on a brake pedal as shown inFIG. 1A. In other examples, controller 12 or a controller linked tocontroller 12 may apply engage wheel brakes. In the same way, africtional force may be reduced to wheels 116 by disengaging wheelbrakes 119 in response to the driver releasing his foot from a brakepedal. Further, vehicle brakes may apply a frictional force to wheels116 via controller 12 as part of an automated engine stopping procedure.

Controller 12 may be configured to receive inputs from engine 10, asshown in more detail in FIG. 1A, and accordingly control a torque outputof the engine and/or operation of the torque converter, transmission,clutches, and/or brakes. As one example, an engine torque output may becontrolled by adjusting a combination of spark timing, fuel pulse width,fuel pulse timing, and/or air charge, by controlling throttle openingand/or valve timing, valve lift and boost for turbo- or super-chargedengines. In the case of a diesel engine, controller 12 may control theengine torque output by controlling a combination of fuel pulse width,fuel pulse timing, and air charge. In all cases, engine control may beperformed on a cylinder-by-cylinder basis to control the engine torqueoutput. Controller 12 may also control torque output and electricalenergy production from DISG by adjusting current flowing to and fromfield and/or armature windings of DISG as is known in the art.

When idle-stop conditions are satisfied, controller 12 may initiateengine shutdown by shutting off fuel and/or spark to the engine.However, the engine may continue to rotate in some examples. Further, tomaintain an amount of torsion in the transmission, the controller 12 mayground rotating elements of transmission 158 to a case 159 of thetransmission and thereby to the frame of the vehicle. When enginerestart conditions are satisfied, and/or a vehicle operator wants tolaunch the vehicle, controller 12 may reactivate engine 10 by craningengine 10 and resuming cylinder combustion.

Intake manifold 44 of engine 10 is in pneumatic communication withvacuum reservoir 177 via valve 176. Vacuum reservoir may provide vacuumto brake booster 178, heating/ventilation/cooling system 179, waste gateactuator 180, and other vacuum operated systems. In one example, valve176 may be a solenoid valve that may be opened and closed to selectivelyallow or prevent communication between intake manifold 44 and vacuumconsumers 178-180. Additionally, a vacuum source 183, such as a pump orejector, may selectively provide vacuum to engine intake manifold 44 sothat if there is leakage through the throttle 62, engine 10 may berestarted with the engine intake manifold pressure being less thanatmospheric pressure. Vacuum source 183 may also selectively supplyvacuum to vacuum consumers 178-180 via three way valve 171, for examplewhen vacuum level in vacuum reservoir 177 is less than a threshold. Thevolume of intake manifold 44 may be adjusted via variable plenum volumevalve 175.

Referring now to FIG. 2A, an example engine configuration of engine 10is shown. In this configuration, engine 10 is an inline four cylinderengine with a first valve configuration. Portions of the engine'scombustion chambers formed in cylinder head casting 35, which also maybe referred to as part of a cylinder, are numbered from 1-4 according tocylinder numbers 1-4 as indicated for each engine cylinder 200. In thisexample, each combustion chamber is shown with two intake valves and twoexhaust valves. Deactivating intake valves 208 are shown as poppetvalves with an X through the poppet valve shaft. Deactivating exhaustvalves 204 are shown as poppet valves with an X through the poppet valveshaft. Non-deactivating intake valves 206 are shown as poppet valves.Non-deactivating exhaust valves 202 are also shown as poppet valves.

Camshaft 270 is shown in mechanical communication with non-deactivatingexhaust valves 202 via non-deactivating exhaust valve operators 250.Camshaft 270 is also in mechanical communication with non-deactivatingintake valves 206 via non-deactivating intake valve operators 251.Camshaft 270 is shown in mechanical communication with deactivatingexhaust valves 204 via deactivating exhaust valve operators 252.Camshaft 270 is also in mechanical communication with deactivatingintake valves 208 via deactivating intake valve operators 253. Someintake and exhaust valves are not shown with valve operators to reducebusyness in the figure, but each valve is accompanied by a valveoperator (e.g., non-deactivating valves are accompanied withnon-deactivating valve operators and deactivating valves are accompaniedwith deactivating valve operators).

In this configuration, cylinders 2 and 3 are shown with deactivatingintake valves 208 and deactivating exhaust valves 204. Cylinders 1 and 4are shown with non-deactivating intake valves 206 and non-deactivatingexhaust valves 202. However, in some examples, non-deactivating intakevalves 206 and non-deactivating exhaust valves 202 may be replaced withdeactivating exhaust valves and deactivating intake valves so that allengine cylinders may be selectively deactivated.

The configuration of FIG. 2A provides for deactivating cylinders 2 and 3together or separately. Further, since both intake and exhaust valves ofcylinders 2 and 3 are deactivating, these cylinders are deactivated byclosing both intake and exhaust valves for an entire engine cycle andceasing fuel flow to cylinders 2 and 3. For example, if the engine has afiring order of 1-3-4-2, the engine may fire in an order of 1-2-1-2, or1-3-2-1-4-2, or 1-3-2-1-3- 2-1-4-2, or other combinations wherecylinders 1 and 2 combust air and fuel. However, if cylinders 1-4 eachincluded deactivating intake and exhaust valves, cylinders 1 and 2 maynot fire (e.g., combust air and fuel) during some engine cycles. Forexample, the engine firing order may be 3-4-3-4, or 1-3-2-1-3-2, or3-4-2-3-4-2, or other combinations where cylinders 1 and 2 do notcombust air and fuel during an engine cycle. It should be noted that adeactivated cylinder may trap exhaust gases or fresh air depending onwhether or not fuel is injected into the cylinder and combusted beforethe exhaust valves are deactivated in a closed position.

FIG. 2A also slows a first knock sensor 203 and a second knock sensor205. First knock sensor 203 is positioned closer to cylinders 1 and 2.Second knock sensor 205 is positioned closer to cylinders 3 and 4. Firstknock sensor may be used to detect knock from cylinders 1 and 2 duringsome conditions and knock from cylinders 1-4 during other conditions.Likewise, second knock sensor 205 may be used to detect knock fromcylinders 3 and 4 during some conditions and knock from cylinders 1-4during other conditions. Alternatively, the knock sensors may bemechanically coupled to the engine block.

Referring now to FIG. 2B, an alternative example engine configuration ofengine 10 is shown. In this configuration, engine 10 is an inline fourcylinder engine with a fraction of cylinders having only deactivatingintake valves. Portions of the engine's combustion chambers formed incylinder head casting 35 are again numbered from 1-4 as indicated forengine cylinders 200. Each cylinder is shown with two intake valves andtwo exhaust valves. Cylinders 1-4 include non-deactivating exhaustvalves 202 and no non-deactivating exhaust valves. Cylinders 1 and 4also include non-deactivating intake valves 206 and no deactivatingintake valves. Cylinders 2 and 3 include deactivating intake valves 208and no non-deactivating intake valves.

Camshaft 270 is shown in mechanical communication with non-deactivatingexhaust valves 202 via non-deactivating exhaust valve operators 250.Camshaft 270 is also in mechanical communication with non-deactivatingintake valves 206 via non-deactivating intake valve operators 251.Camshaft 270 is also in mechanical communication with deactivatingintake valves 208 deactivating intake valve operators 253. Some intakeand exhaust valves are not shown with valve operators to reduce busynessin the figure, but each valve is accompanied by a valve operator (e.g.,non-deactivating valves are accompanied with non-deactivating valveoperators and deactivating valves are accompanied with deactivatingvalve operators).

The configuration of FIG. 2B provides for deactivating cylinders 2 and 3together or separately via deactivating intake valves 208. The exhaustvalves of cylinders 2 and 3 continue to open and close during an enginecycle as the engine rotates. Further, since only intake valves ofcylinders 2 and 3 deactivate, these cylinders are deactivated by closingonly intake valves for an entire engine cycle and ceasing fuel flow tocylinders 2 and 3. Once again, if the engine has a firing order of1-3-4-2, the engine may fire in an order of 1-2-1-2, or 1-3-2-1-4-2, or1-3-2-1-3-2-1-4-2, or other combinations where cylinders 1 and 2 combustair and fuel. It should be noted that a deactivated cylinder in thisconfiguration pulls exhaust into itself and expels exhaust during thedeactivated cylinder's exhaust stroke. Specifically, exhaust is drawninto the deactivated cylinder when the deactivated cylinder's exhaustvalve opens near the beginning of the exhaust stroke, and exhaust isexpelled from the deactivated cylinder when the cylinder's pistonapproaches top-dead-center exhaust stroke before the exhaust valvecloses.

In other examples, cylinders 1 and 4 may include the deactivating intakevalves while cylinders 2 and 3 include non-deactivating intake valves.Otherwise, the valve arrangement may be the same.

Referring now to FIG. 2C, another alternative example engineconfiguration of engine 10 is shown. In this configuration, engine 10 isan inline four cylinder engine and all engine cylinders includedeactivating intake valves 208, and none of the cylinders includedeactivating exhaust valves. Portions of the engine's combustionchambers formed in cylinder head casting 35 are again numbered from 1-4as indicated for engine cylinders 200. Each cylinder is shown with twointake valves and two exhaust valves. Cylinders 1-4 include deactivatingintake valves 208 and no deactivating intake valves. Cylinders 1-4 alsoinclude non-deactivating exhaust valves 202 and no deactivating exhaustvalves. Engine 10 is also shown with first knock sensor 220 and secondknock sensor 221.

Camshaft 270 is shown in mechanical communication with non-deactivatingexhaust valves 202 via non-deactivating exhaust valve operators 250.Camshaft 270 is also in mechanical communication with deactivatingintake valves 208 deactivating intake valve operators 253. Some intakeand exhaust valves are not shown with valve operators to reduce busynessin the figure, but each valve is accompanied by a valve operator (e.g.,non-deactivating valves are accompanied with non-deactivating valveoperators and deactivating valves are accompanied with deactivatingvalve operators).

The configuration of FIG. 2C provides for deactivating cylinders 1-4 inany combination during an engine cycle via deactivating only intakevalves of cylinders 1-4. The exhaust valves of cylinders 1-4 continue toopen and close during an engine cycle as the engine rotates. Further,cylinders 1-4 may be deactivated by closing only intake valves for anentire engine cycle and ceasing fuel flow to cylinders 1-4, orcombinations thereof. If the engine has a firing order of 1-3-4-2, theengine may fire in an order of 1-2-1-2, or 1-3-2-1-4-2, or1-3-2-1-3-2-1- 4-2, or other combinations of cylinders 1-4 since eachcylinder may be deactivated individually without deactivating otherengine cylinders. It should be noted that a deactivated cylinder in thisconfiguration pulls exhaust into itself and expels exhaust during thedeactivated cylinder's exhaust stroke. Specifically, exhaust is drawninto the deactivated cylinder when the deactivated cylinder's exhaustvalve opens near the beginning of the exhaust stroke, and exhaust isexpelled from the deactivated cylinder when the cylinder's pistonapproaches top-dead-center exhaust stroke before the exhaust valvecloses.

Referring now to FIG. 2D, another alternative engine configuration ofengine 10 is shown. The system of FIG. 2D is identical to the system ofFIG. 2A, except the system of FIG. 2D includes an intake camshaft 271and an exhaust camshaft 272. Portions of the engine's combustionchambers formed in cylinder head casting 35, which also may be referredto as part of a cylinder, are numbered from 1-4 according to cylindernumbers 1-4 as indicated for each engine cylinder 200.

Camshaft 271 is shown in mechanical communication with non-deactivatingexhaust valves 202 via non-deactivating exhaust valve operators 250.Camshaft 272 is in mechanical communication with non-deactivating intakevalves 206 via non-deactivating intake valve operators 251. Camshaft 271is shown in mechanical communication with deactivating exhaust valves204 via deactivating intake valve operators 252. Camshaft 272 is inmechanical communication with deactivating intake valves 208 viadeactivating intake valve operators 253. Some intake and exhaust valvesare not shown with valve operators to reduce busyness in the figure, buteach valve is accompanied by a valve operator (e.g., non-deactivatingvalves are accompanied with non-deactivating valve operators anddeactivating valves are accompanied with deactivating valve operators).

Referring now to FIG. 2E, another alternative engine configuration ofengine 10 is shown. The system of FIG. 2E is identical to the system ofFIG. 2B, except the system of FIG. 2E includes an intake camshaft 271and an exhaust camshaft 272. Portions of the engine's combustionchambers formed in cylinder head casting 35, which also may be referredto as part of a cylinder, are numbered from 1-4 according to cylindernumbers 1-4 as indicated for each engine cylinder 200.

Camshaft 271 is shown in mechanical communication with non-deactivatingexhaust valves 202 via non-deactivating exhaust valve operators 250.Camshaft 272 is in mechanical communication with non-deactivating intakevalves 206 via non-deactivating intake valve operators 251. Camshaft 272is also in mechanical communication with deactivating intake valves 208deactivating intake valve operators 253. Some intake and exhaust valvesare not shown with valve operators to reduce busyness in the figure, buteach valve is accompanied by a valve operator (e.g., non-deactivatingvalves are accompanied with non-deactivating valve operators anddeactivating valves are accompanied with deactivating valve operators).

Referring now to FIG. 2F, another alternative engine configuration ofengine 10 is shown. The system of FIG. 2F is identical to the system ofFIG. 2C, except the system of FIG. 2F includes an intake camshaft 271and an exhaust camshaft 272. Portions of the engine's combustionchambers formed in cylinder head casting 35, which also may be referredto as part of a cylinder, are numbered from 1-4 according to cylindernumbers 1-4 as indicated for each engine cylinder 200.

Camshaft 271 is shown in mechanical communication with non-deactivatingexhaust valves 202 via non-deactivating exhaust valve operators 250.Camshaft 272 is in mechanical communication with deactivating intakevalves 208 deactivating intake valve operators 253. Some intake andexhaust valves are not shown with valve operators to reduce busyness inthe figure, but each valve is accompanied by a valve operator (e.g.,non-deactivating valves are accompanied with non-deactivating valveoperators and deactivating valves are accompanied with deactivatingvalve operators).

The deactivating valve operators shown in FIGS. 2A-2F may be a levertype (e.g., see FIG. 6B), a sleeve type (e.g., see U.S. PatentPublication No. 2014/0303873, U.S. patent application Ser. No.14/105,000, entitled “Position Detection For Lobe Switching CamshaftSystem,” filed Dec. 12, 2013 and hereby fully incorporated by referencefor all purposes), a cam lobe type, or a lash adjuster type. Further,each of the cylinder heads shown in FIGS. 2A-2F may be mechanicallycoupled to a same block 33 shown in FIG. 1A. The cylinder heads shown inFIGS. 2A-2F may be formed from a same casting and the deactivating andnon-deactivating valve operators for each cylinder head configurationmay be varied as shown in FIGS. 2A-2F.

Referring now to FIG. 3A, an example cylinder deactivation pattern isshown. In FIG. 3A, cylinder 4 of engine 10 is shown with an X through itto indicate that cylinder 4 may be deactivated during an engine cyclewhile cylinders 1, 2, and 3 remain active. Active cylinders are shownwithout Xs to indicate the cylinders are active. One cylinder may bedeactivated during an engine cycle via the system shown in FIG. 2C. Asan alternative, cylinder 1 may be the only deactivated cylinder duringan engine cycle when engine 10 is configured as is shown in FIG. 2C.Cylinder 2 may be the only deactivated cylinder during an engine cyclewhen engine 10 is configured as is shown in FIGS. 2A, 2B, and 2C.Likewise, cylinder 3 may be the only deactivated cylinder during anengine cycle when engine 10 is configured as is shown in FIGS. 2A, 2B,and 2C. Cylinders 200 are shown in a line.

Referring now to FIG. 3B, another example cylinder deactivation patternis shown. In FIG. 3B, cylinders 2 and 3 of engine 10 is shown with Xsthrough them to indicate that cylinder 2 and 3 may be deactivated duringan engine cycle while cylinders 1 and 4 remain active. Active cylindersare shown without Xs to indicate the cylinders are active. Cylinders 2and 3 may be deactivated during an engine cycle via the systems shown inFIGS. 2A, 2B, and 2C. As an alternative, cylinders 1 and 4 may be theonly deactivated cylinder during an engine cycle when engine 10 isconfigured as is shown in FIG. 2C. Deactivated cylinders shown in FIGS.2 and 3 are cylinders where valves are closed to prevent flow from theengine intake manifold to the engine exhaust manifold while the enginerotates and where fuel injection ceases to the deactivated cylinders.Spark provided to deactivated cylinders may also cease. Cylinders 200are shown in a line.

In this way, individual cylinders or cylinder groups may be deactivated.Further, deactivated cylinders may be reactivated from time to time toreduce the possibility of engine oil seeping into engine cylinders. Forexample, a cylinder may fire 1-4-1-4-1-4-2-1-4-3-1-4-1-4 to reduce thepossibility of oil seeping into cylinders 2 and 3 after cylinders 2 and3 have been deactivated.

Referring now to FIG. 4A, another example configuration of engine 10 isshown. Portions of the engine's combustion chambers formed in cylinderheads 35 and 35 a, which also may be referred to as part of a cylinder,are numbered from 1-8 according to cylinder numbers 1-8 as indicated foreach engine cylinder. Engine 10 includes a first bank of cylinders 401including cylinders 1-4 in cylinder head casting 35 and a second bank ofcylinders 402 including cylinders 5-8 in cylinder head casting 35 a. Inthis configuration, engine 10 is a V eight engine that includesdeactivating intake valves 208 and non-deactivating intake valves 206.Engine 10 also includes deactivating exhaust valves 204 andnon-deactivating exhaust valves 202. The valves control air flow fromthe engine intake manifold to the engine exhaust manifold via enginecylinders 200. In some examples, deactivating exhaust valves 204 may bereplaced with non-deactivating exhaust valves 202 to reduce systemexpense while preserving the capacity to deactivate engine cylinders(e.g., cease fuel flow to the deactivated cylinder and cease air flowfrom an engine intake manifold to engine exhaust manifold via a cylinderwhile the engine rotates). Thus, in some examples, engine 10 may includeonly non-deactivating exhaust valves 202 in combination withdeactivating intake valves 208 and non-deactivating intake valves 206.

In this example, cylinders 5, 2, 3, and 8 are shown as cylinders thathave valves that are always active so that air flows from the engineintake manifold to the engine exhaust manifold as the engine rotates viacylinders 5, 2, 3, and 8. Cylinders 1, 6, 7, and 4 are shown ascylinders that have valves that may be selectively deactivated in closedpositions so that air does not flow from the engine intake manifold tothe engine exhaust manifold via cylinders 1, 6, 7, and 4 respectivelywhen valves in the respective cylinders are deactivated in a closedstate during an engine cycle. In other examples, such as FIG. 4B, thecylinders that have valves that are always active are cylinders 5 and 2.The actual total number of cylinders that have valves that are alwaysactive may be based on vehicle mass and engine displacement or otherconsiderations.

Valves 202, 204, 206, and 208 are opened and closed via a singlecamshaft 420. The valves 202, 204, 206, and 208 may be in mechanicalcommunication with sole camshaft 320 via pushrods and conventional lashadjusters or deactivating adjusters or hydraulic cylinders as shown inU.S. Patent Publication No. 2003/0145722, entitled “Hydraulic CylinderDeactivation with Rotary Sleeves,” filed Feb. 1, 2002 and hereby fullyincorporated by reference for all purposes. Alternatively, valves 202,204, 206, and 208 may be operated via conventional roller cam followersand/or via valve operators as shown in FIGS. 6A, 6B, and 5C. In stillother examples, valves may be deactivated via sleeved cam lobes as shownin U.S. Patent Publication No. 2014/0303873.

Camshaft 420 is shown in mechanical communication with non-deactivatingexhaust valves 202 via non-deactivating exhaust valve operators 250.Camshaft 420 is also in mechanical communication with non-deactivatingintake valves 206 via non-deactivating intake valve operators 251.Camshaft 420 is also in mechanical communication with deactivatingintake valves 208 deactivating intake valve operators 253. Camshaft 420is also in mechanical communication with deactivating exhaust valves 204via deactivating intake valve operators 252. Some intake and exhaustvalves are not shown with valve operators to reduce busyness in thefigure, but each valve is accompanied by a valve operator (e.g.,non-deactivating valves are accompanied with non-deactivating valveoperators and deactivating valves are accompanied with deactivatingvalve operators).

Referring now to FIG. 4B, another example configuration of engine 10 isshown. Portions of the engine's combustion chambers formed in cylinderheads 35 and 35 a, which also may be referred to as part of a cylinder,are numbered from 1-8 according to cylinder numbers 1-8 as indicated foreach engine cylinder. Engine 10 includes a first bank of cylinders 401including cylinders 1-4 in cylinder head casting 35 and a second bank ofcylinders 402 including cylinders 5-8 in cylinder head casting 35 a. Inthis configuration, engine 10 is also a V eight engine that includesdeactivating intake valves 208 and non-deactivating intake valves 206.Engine 10 also includes deactivating exhaust valves 204 andnon-deactivating exhaust valves 202. The valves control air flow fromthe engine intake manifold to the engine exhaust manifold via enginecylinders 200. Valves 202, 204, 206, and 208 are operated via intakecamshaft 51 and exhaust camshaft 53. Each cylinder bank includes anintake camshaft 51 and an exhaust camshaft 53.

In some examples, deactivating exhaust valves may be replaced withnon-deactivating exhaust valves 204 to reduce system expense whilepreserving the capacity to deactivate engine cylinders (e.g., cease fuelflow to the deactivated cylinder and cease air flow from an engineintake manifold to engine exhaust manifold via a cylinder while theengine rotates). Thus, in some examples, engine 10 may include onlynon-deactivating exhaust valves 202 in combination with deactivatingintake valves 208 and non-deactivating intake valves 206.

In this example, cylinders 5 and 2 are shown as cylinders that havevalves that are always active so that air flows from the engine intakemanifold to the engine exhaust manifold as the engine rotates viacylinders 5 and 2. Cylinders 1, 3, 4, 6, 7, and 8 are shown as cylindersthat have intake and exhaust valves that may be selectively deactivatedin closed positions so that air does not flow from the engine intakemanifold to the engine exhaust manifold via cylinders 1, 3, 4, 6, 7, and8 respectively when valves in the respective cylinders are deactivatedin a closed state. In this example, cylinders are deactivated bydeactivating intake and exhaust valves of the cylinder beingdeactivated. For example, cylinder 3 may be deactivated so that air doesnot flow through cylinder 3 via deactivating valves 208 and 204.

Valves 202, 204, 206, and 208 are opened and closed via four camshafts.The valves 202, 204, 206, and 208 may be in mechanical communicationwith a camshaft via valve operators shown in FIGS. 6A, 6B, and 5C orhydraulic cylinders or tappets, which may deactivate the valves. Theengines shown in FIGS. 4A and 4B have a firing order of 1-5-4-2-6-3-7-8.

Engine 10 is also shown with first knock sensor 420, second knock sensor421, third knock sensor 422, and fourth knock sensor 423. Thus, firstcylinder bank 401 includes first knock sensor 420 and second knocksensor 421. First knock sensor 420 may detect knock in cylinder numbers1 and 2. Second knock sensor 421 may detect knock in cylinder numbers 3and 4. Second cylinder bank 402 includes third knock sensor 422 andfourth knock sensor 423. Third knock sensor 422 may detect knock incylinders 5 and 6. Fourth knock sensor 423 may detect knock in cylinders7 and 8.

Exhaust camshaft 53 is shown in mechanical communication withnon-deactivating exhaust valves 202 via non-deactivating exhaust valveoperators 250 Intake camshaft 51 is in mechanical communication withnon-deactivating intake valves 206 via non-deactivating intake valveoperators 251. Exhaust camshaft 53 is also in mechanical communicationwith deactivating exhaust valves 204 deactivating intake valve operators252 Intake camshaft 51 is also in mechanical communication withdeactivating intake valves 208 via deactivating intake valve operators253. Some intake and exhaust valves are not shown with valve operatorsto reduce busyness in the figure, but each valve is accompanied by avalve operator (e.g., non-deactivating valves are accompanied withnon-deactivating valve operators and deactivating valves are accompaniedwith deactivating valve operators).

The cylinder head configuration shown in FIG. 4B may be incorporated invehicles of lower mass than the vehicles in which the cylinder headconfiguration shown in FIG. 4A is included. The configuration of FIG. 4Bmay be incorporated in vehicle of low mass since lower mass vehicles mayonly use two cylinders to cruise at a steady highway speed. Conversely,the configuration of FIG. 4A may be incorporated in vehicles of highermass since vehicle's having a higher mass may use four cylinders tocruise at a steady highway speed. Likewise, the cylinder heads shown inFIGS. 2A-2F that have lower actual total numbers of cylinders that arenot deactivating may be incorporated into lower mass vehicles. Thecylinder heads shown in FIGS. 2A-2F that have higher actual totalnumbers of cylinders that are not deactivating may be incorporated intohigher mass vehicles. Additionally, the number of cylinders in cylinderhead castings shown in FIGS. 2A-4C that are not deactivating cylindersmay be based on the vehicle's axle ratio. For example, if a vehicle hasa lower axle ratio (e.g., 2.69:1 versus 3.73:1), a cylinder headconfiguration with a lower actual total number of cylinders that are notdeactivating may be selected so that highway cruising efficiency may beimproved. Thus, different vehicles with different masses and axle ratiosmay include a same engine block and cylinder head castings, but theactual total number of deactivating and non-deactivating valve operatorsmay be different between the different vehicles.

Referring now to FIG. 4C, another example configuration of engine 10 isshown. Portions of the engine's combustion chambers formed in cylinderheads 35 and 35 a, which also may be referred to as part of a cylinder,are numbered from 1-8 according to cylinder numbers 1-8 as indicated foreach engine cylinder. Engine 10 includes a first bank of cylinders 401including cylinders 1-4 in cylinder head casting 35 and a second bank ofcylinders 402 including cylinders 5-8 in cylinder head casting 35 a. Inthis configuration, engine 10 is also a V eight engine that includesdeactivating intake valves 208 and non-deactivating intake valves 206.Engine 10 also includes non-deactivating exhaust valves 202. The valvescontrol air flow from the engine intake manifold to the engine exhaustmanifold via engine cylinders 200. Valves 202, 206, and 208 are operatedvia intake camshaft 51 and exhaust camshaft 53. Each cylinder bankincludes an intake camshaft 51 and an exhaust camshaft 53.

In this example, all engine exhaust valves 202 are non-deactivating.Exhaust camshaft 53 is shown in mechanical communication withnon-deactivating exhaust valves 202 via non-deactivating exhaust valveoperators 250 Intake camshaft 51 is in mechanical communication withnon-deactivating intake valves 206 via non-deactivating intake valveoperators 251 Intake camshaft 51 is also in mechanical communicationwith deactivating intake valves 208 via deactivating intake valveoperators 253. Some intake and exhaust valves are not shown with valveoperators to reduce busyness in the figure, but each valve isaccompanied by a valve operator (e.g., non-deactivating valves areaccompanied with non-deactivating valve operators and deactivatingvalves are accompanied with deactivating valve operators).

The deactivating valve operators shown in FIGS. 4A-4C may be a levertype (e.g., see FIG. 6B), a sleeve type (e.g., see U.S. PatentPublication No. 2014/0303873, U.S. patent application Ser. No.14/105,000, entitled “Position Detection For Lobe Switching CamshaftSystem,” filed Dec. 12, 2013 and hereby fully incorporated by referencefor all purposes), a cam lobe type, or a lash adjuster type. Further,each of the cylinder heads shown in FIGS. 4A-4C may be mechanicallycoupled to a same block 33 shown in FIG. 1A. The cylinder heads 35 shownin FIGS. 4A-4C may be formed from a same casting and the deactivatingand non-deactivating valve operators for each cylinder headconfiguration may be varied as shown in FIGS. 4A-4C. Likewise, thecylinder heads 35 a shown in FIGS. 4A-4C may be formed from a samecasting and the deactivating and non-deactivating valve operators foreach cylinder head configuration may be varied as shown in FIGS. 4A-4C.

Referring now to FIG. 5A, an example valve operating system is shown.The depicted embodiment may represent a mechanism for an inline fourcylinder engine or one of two mechanisms for a V-8 engine. Similarmechanisms with for different numbers of engine cylinders are possible.Valve operating system 500 includes an intake camshaft 51 and an exhaustcamshaft 53. Chain, gear, or belt, 599 mechanically couples camshaft 51and camshaft 53 so that they rotate together at a same speed. Inparticular, chain 599 mechanically couples sprocket 520 to sprocket 503.

Exhaust camshaft 53 includes cylindrical journals 504 a, 504 b, 504 c,and 504 d that rotate within respective valve bodies 501 a, 501 b, 501c, and 501 d. Valve bodies 501 a, 501 b, 501 c, and 501 d are shownincorporated into exhaust camshaft saddle 502, which may be part ofcylinder head casting 35. Discontinuous metering grooves 571 a, 571 b,571 c, and 571 d are incorporated into journals 504 a, 504 b, 504 c, and504 d. Discontinuous metering grooves 571 a, 571 b, 571 c, and 571 d maybe aligned with crankshaft 40 shown in FIG. 1A to allow oil flow throughjournals 504 a, 504 b, 504 c, and 504 d coincident with a desired enginecrankshaft angle range so that exhaust valve operators shown in FIG. 5Bare deactivated at a desired crankshaft angle, thereby ceasing airflowfrom engine cylinders. Lands 505 a, 505 b, 505 c, and 505 d prevent oilflow to valve operators shown in FIG. 5B when the respective lands coverrespective valve body outlets 506, 508, 510, and 512.

Oil may flow to valve operators shown in FIG. 5B via valve body outlets506, 508 510 and 512. Pressurized oil from oil pump 580 may selectivelypass through valve body inlets 570, 572, 574, and 576; metering grooves571 a, 571 b, 571 c, and 571 d; and valve body outlets when lands arenot blocking valve body inlets and outlets 506, 508, 510 and 512. Thepressurized oil may deactivate valve operators as described in furtherdetail below. Lands 505 a, 505 b, 505 c, and 505 d selectively open andclose access to valve bodies 501 a, 501 b, 501 c, and 501 d forpressurized oil from oil pump 580 as exhaust camshaft 53 rotates.Exhaust camshaft 53 also includes cam lobes 507 a, 507 b, 509 a, 509 b,511 a, 511 b, 513 a, and 513 b to open and close exhaust valves as lobelift increases and decreases in response to exhaust camshaft rotation.

In one example, pressurized oil selectively flows through meteringgroove 571 a via valve body inlet 570 to exhaust valve operators forcylinder number one. Cam lobes 507 a and 507 b may provide mechanicalforce to lift exhaust valves of cylinder number one of a four or eightcylinder engine as exhaust camshaft 53 rotates. Similarly, pressurizedoil selectively flows through metering groove 571 b via valve body inlet572 to exhaust valve operators for cylinder number two. Cam lobes 509 aand 509 b may provide mechanical force to lift exhaust valves ofcylinder number two of the four or eight cylinder engine as exhaustcamshaft 53 rotates. Likewise, pressurized oil selectively flows throughmetering groove 571 c via valve body inlet 574 to exhaust valveoperators for cylinder number three. Cam lobes 511 a and 511 b mayprovide mechanical force to lift exhaust valves of cylinder number threeof a four or eight cylinder engine as exhaust camshaft 53 rotates. Also,pressurized oil selectively flows through metering groove 571 d viavalve body inlet 576 to exhaust valve operators for cylinder numberfour. Cam lobes 513 a and 513 b may provide mechanical force to liftexhaust valves of cylinder number four of a four or eight cylinderengine as exhaust camshaft 53 rotates. Thus, exhaust camshaft 53 mayprovide force to open poppet valves of a cylinder bank.

Intake camshaft 51 includes cylindrical journals 521 a, 521 b, 521 c,and 521 d that rotate within respective valve bodies 540 a, 540 b, 540c, and 540 d. Valve bodies 540 a, 540 b, 540 c, and 540 d are shownincorporated into intake camshaft saddle 522, which may be part ofcylinder head casting 35. Continuous metering grooves 551 a, 551 b, 551c, and 551 d are incorporated into journals 521 a, 521 b, 521 c, and 521d. However, in some examples, continuous metering grooves 551 a, 551 b,551 c, and 551 d may be eliminated and oil may be supplied directly frompump 580 to intake valve operators.

Pressurized oil flows from oil pump 580 via passage or gallery 581 tocontrol valves 586, 587, 588, and 589. Control valve 586 may be openedto allow oil to flow into valve body inlet 550, metering groove 551 a,and valve body outlet 520 a before oil flows to cylinder number oneintake valve operators via passage 520 b. Pressurized oil is alsosupplied to inlet 570 via passage or conduit 524 c. Thus, by closingvalve 586, deactivation of intake valves and exhaust valves of cylindernumber one may be prevented. Outlet 506 supplies oil to accumulator 506b and to exhaust valve operators for cylinder number one.

Selective operation of intake and exhaust valves for cylinder number twois similar to selective operation of intake and exhaust valves forcylinder number one. Specifically, pressurized oil flows from oil pump580 via passage or gallery 581 to valve 587, which may be opened toallow oil to flow into valve body inlet 552, metering groove 551 b, andvalve body outlet 524 a before oil flows to cylinder number two intakevalve operators via passage 524 b. Pressurized oil is also supplied tovalve body inlet 572 via passage or conduit 524 c. Thus, by closingvalve 587, deactivation of intake valves and exhaust valves of cylindernumber two may be prevented. Outlet 508 supplies oil to accumulator 508b and to exhaust valve operators for cylinder number two.

Selective operation of intake and exhaust valves for cylinder numberthree is similar to selective operation of intake and exhaust valves forcylinder number one. For example, pressurized oil flows from oil pump580 via passage or gallery 581 to valve 588, which may be opened toallow oil to flow into valve body inlet 554, metering groove 551 c, andvalve body outlet 526 a before oil flows to cylinder number three intakevalve operators via passage 526 b. Pressurized oil is also supplied tovalve body inlet 574 via passage or conduit 526 c. Thus, by closingvalve 588, deactivation of intake valves and exhaust valves of cylindernumber three may be prevented. Outlet 510 supplies oil to accumulator510 b and to exhaust valve operators for cylinder number three.

Selective operation of intake and exhaust valves for cylinder numberfour is also similar to selective operation of intake and exhaust valvesfor cylinder number one. In particular, pressurized oil flows from oilpump 580 via passage or gallery 581 to valve 589, which may be opened toallow oil to flow into valve body inlet 556, metering groove 551 d, andvalve body outlet 528 a before oil flows to cylinder number four intakevalve operators via passage 528 b. Pressurized oil is also supplied tocontrol valve body inlet 576 via passage or conduit 528 c. Thus, byclosing valve 589, deactivation of intake valves and exhaust valves ofcylinder number four may be prevented. Outlet 512 supplies oil toaccumulator 512 b and to exhaust valve operators for cylinder numberfour.

Intake valve operators shown in FIG. 5B may be urged by cam lobes 523a-529 b to operate intake valves of a bank of cylinders. In particular,cam lobes 523 a and 523 b respectively operate two intake valves ofcylinder number one. Cam lobes 525 a and 525 b respectively operate twointake valves of cylinder number two. Cam lobes 527 a and 527 brespectively operate two intake valves of cylinder number three. Camlobes 529 a and 529 b respectively operate two intake valves of cylindernumber four.

Thus, intake and exhaust valves of a cylinder bank may be individuallyactivated and deactivated. Further, in some examples as previouslynoted, oil may be supplied directly from valves 586-589 to intake valveoperators such that continuous metering grooves 551 a-551 d may beomitted to reduce system cost if desired.

Oil pump 580 also supplies oil to cooling jet 535 to spray piston 36shown in FIG. 1A via cooling jet flow control valve 534. Oil pressure ingallery 581 may be controlled via dump valve 532 or via adjusting oilpump displacement actuator 533 which adjusts the displacement of oilpump 580. Controller 12 shown in FIG. 1A may be in electricalcommunication with cooling jet flow control valve 534, oil pumpdisplacement actuator 533, and dump valve 532. Oil pump displacementactuator may be a solenoid valve, a linear actuator, or other knowndisplacement actuator.

Referring now to FIG. 5B, example deactivating intake valve operator 549and exhaust valve operator 548 for the hydraulically operated valvedeactivating system shown in FIG. 5A are shown. Intake camshaft 51rotates so that lobe 523 a selectively lifts intake follower 545, whichselectively opens and closes intake valve 52. Rocker shaft 544 providesa selective mechanical linkage between intake follower 545 and intakevalve contactor 547. Passage 546 allows pressurized oil to reach apiston shown in FIG. 5C so that intake valve 52 may be deactivated(e.g., remain in a closed position during an engine cycle) Intake valve52 may be activated when oil pressure in passage 546 is low.

Similarly, Exhaust camshaft 53 rotates so that lobe 507 a selectivelylifts exhaust follower 543, which selectively opens and closes exhaustvalve 54. Rocker shaft 542 provides a selective mechanical linkagebetween exhaust follower 543 and exhaust valve contactor 540. Passage541 allows oil to reach a piston shown in FIG. 5C so that exhaust valve54 may be activated (e.g., open and close during an engine cycle) ordeactivated (e.g., remain in a closed position during an engine cycle).

Referring now to FIG. 5C, an example exhaust valve operator 548 is shownIntake valve operators include similar components and operate similar tothe way the exhaust valve actuator operates. Therefore, for the sake ofbrevity, a description of intake valve operators is omitted.

Exhaust follower 543 is shown with oil passage 565, which extends withincamshaft follower 564. Oil passage 565 fluidly communicates with port568 in rocker shaft 542. Piston 563 and latching pin 561 selectivelylock follower 543 to exhaust valve contactor 540, which causes exhaustvalve contactor 540 to move in response to the motion of follower 543when oil is not acting on piston 563. The exhaust valve operator 548 isin an activated state during such conditions.

Piston 563 may be acted upon by oil pressure within oil passages 567 and565. Piston 563 is forced from its at-rest position shown in FIG. 5C(e.g., its normally activated state) by high pressure oil in passage 565acting against force of spring 569 to its deactivated state. Spring 565biases piston 563 into a normally locked position that allows exhaustvalve contactor 540 to operate an exhaust valve 54 when oil pressure inpassage 565 is low.

Latching pin 561 stops at a position (e.g., unlocked position) wherefollower 543 is no longer locked to exhaust valve contactor 540, therebydeactivating exhaust valve 54 when normally locked latching pin 561 isfully displaced by high pressure oil operating on piston 563. Camshaftfollower 564 is rocked according to the movement of cam lobe 507 a whenexhaust valve operator 548 is in a deactivated state. Exhaust valve 54and exhaust valve contactor 540 remain stationary when piston latchingpin 561 is in its unlocked position.

Thus, oil pressure may be used to selectively activate and deactivateintake and exhaust valves via intake and exhaust valve operators.Specifically, intake and exhaust valves may be deactivated by allowingoil to flow to the intake and exhaust valve operators. It should benoted that intake and exhaust valve operators may be activated anddeactivated via the mechanism shown in FIG. 5C. FIGS. 5B and 5C depictrocker shaft mounted deactivating valve actuators. Other types ofdeactivating valve actuators are possible and compatible with theinvention including deactivating roller finger followers, deactivatinglifters, or deactivating lash adjusters.

Referring now to FIG. 5D, a valve and cylinder deactivation sequence forthe mechanism of FIGS. 5A-5C is shown. The valve deactivation sequencemay be provided by the system of FIGS. 1A and 5A-5C.

The first plot from the top of FIG. 5D is a plot of exhaust cam groovewidth versus crankshaft angle. The vertical axis represents exhaustcamshaft groove width measured at the location of the oil outletpassage, such as passage 506 of FIG. 5A. Groove width increases in thedirection of the vertical axis arrow. The horizontal axis representsengine crankshaft angle, where zero is top-dead-center compressionstroke for the cylinder whose intake and exhaust grooves are shown. Inthis example, the exhaust groove corresponds to 571 a of FIG. 5A. Thecrankshaft angles for the exhaust groove width are the same as thecrankshaft angle in the third plot from the top of FIG. 5D.

The second plot from the top of FIG. 5D is a plot of intake cam groovewidth versus crankshaft angle. The vertical axis represents intakecamshaft groove width and groove width increases in the direction of thevertical axis arrow. The horizontal axis represents engine crankshaftangle, where zero is top-dead-center compression stroke for the cylinderwhose intake and exhaust grooves are shown. In this example, the intakegroove corresponds to 551 a of FIG. 5A. The crankshaft angles for theintake groove width are the same as the crankshaft angle in the thirdplot from the top of FIG. 5D.

The third plot from the top of FIG. 5D is a plot of intake and exhaustvalve lift versus engine crankshaft angle. The vertical axis representsvalve lift and valve lift increases in the direction of the verticalaxis arrow. The horizontal axis represents engine crankshaft angle andthe three plots are aligned according to crankshaft angle. Thin solidline 590 represents intake valve lift for cylinder number one when itsintake valve operator is activated. Thick solid line 591 representsexhaust valve lift for cylinder number one when its exhaust valveoperator is activated. Thin dashed lines 592 represent intake valve liftfor cylinder number one if its intake valve operator were activated.Thin dashed line 593 represents exhaust valve lift for cylinder numberone if its exhaust valve operator were activated. Vertical lines A-Drepresent crankshaft angles of interest for the sequence.

The intake valve lift for cylinder number one is shown increasing andthen decreasing before crankshaft angle A. An oil control valve, such as586 of FIG. 5A, is closed before crankshaft angle A to prevent intakeand exhaust valve deactivation. The intake valve lift 590 is shownincreasing during cylinder number one's intake stroke before crankshaftangle A. Pressurized oil sufficient to deactivate intake valves is notpresent in the continuous intake camshaft groove before crankshaft angleA.

At crankshaft angle A, the oil control valve (e.g., 586 of FIG. 5A) maybe opened to deactivate intake and exhaust valves. The continuous intakecamshaft groove width is pressurized with oil after the oil controlvalve is opened so that the intake valve operator latching pin may bedisplaced while the camshaft lobe is on a base circle for the intakevalve of cylinder number one. The exhaust camshaft groove 571 a is alsopressurized with oil at crankshaft angle A. Outlet passage 506 is notpressurized with oil at angle A because the land 505 a (shown in FIG.5A) covers the valve body outlet 506 (shown in FIG. 5A). Therefore, onlythe intake valve begins to be deactivated at crankshaft angle A. Theintake valve operator latching pin is disengaged from its normalposition before crankshaft angle C to prevent the intake valve fromopening.

At crankshaft angle B, the land of the exhaust camshaft journal 521 afor cylinder number one makes way for the discontinuous groove 571 a,which allows oil to reach the exhaust valve operator for cylinder numberone. Oil can flow to the intake valve operator and the exhaust valveoperator at crankshaft angle B, but since the exhaust valve is partiallylifted at crankshaft angle B, the exhaust valve operates until theexhaust valve closes near crankshaft angle C. The exhaust valve operatorlatching pin is disengaged from its normally engaged position beforecrankshaft angle D to prevent the exhaust valve from opening.

At crankshaft angle C, the intake valve does not open since the intakevalve operator is deactivated for the engine cycle. Further, the exhaustvalve operator latching pin is disengaged from its normal positionbefore crankshaft angle D to prevent the exhaust valve from opening.Consequently, the exhaust valve does not open for the cylinder cycle.The intake and exhaust valves may remain deactivated until the intakeand exhaust operators are reactivated by reducing oil pressure to theintake and exhaust valve operators.

The intake and exhaust valve may be reactivated via deactivating the oilcontrol valve 586 and allowing oil pressure in the intake and exhaustvalve operators to be reduced or via dumping oil pressure from theintake and exhaust valve operators via a dump valve (not shown).

Oil accumulator 506 b maintains oil pressure in oil passage 506 duringthe portion of the cycle after crankshaft angle D when the exhaust camgroove land blocks passage 506. The accumulator 506 b compensates foroil leakage through various clearances during the time when oil supplyfrom the pump is interrupted. The oil accumulator 506 b may include adedicated piston and spring or may be combined with the latch pinmechanism such as the mechanism depicted in FIG. 5C.

Referring now to FIG. 6A, a camshaft for an alternative hydraulicallyoperated valve deactivating system is shown. Camshaft 420 may beincluded in the engine system shown in FIG. 4A.

In this example, camshaft 420 may be an intake camshaft or an exhaustcamshaft or a camshaft that operates both intake and exhaust valves. Theintake and exhaust valves of each engine cylinder may be individuallyactivated and deactivated. Camshaft 420 includes sprocket 619 thatallows crankshaft 40 of FIG. 1A to drive camshaft 420 via a chain.Camshaft 420 includes four journals 605 a-605 d, which include lands 606a-606 d, and discontinuous grooves 608 a-608 d. Camshaft saddle 602includes stationary grooves 610 a (shown in FIG. 6B) for each of valvebodies 670 a, 670 b, 670 c, and 670 d. The stationary grooves 610 a aresituated to axially align with discontinuous grooves 608 a-608 d.Camshaft 420 also includes cam lobes. In one example, camshaft 420 mayoperate both intake and exhaust valves as camshaft 420 rotates. Inparticular, lobe 620 operates an intake valve of cylinder number one andlobe 622 operates an exhaust valve of cylinder number one. Lobe 638operates an intake valve of cylinder number two and lobe 639 operates anexhaust valve of cylinder number two. Lobe 648 operates an intake valveof cylinder number three and lobe 649 operates an exhaust valve ofcylinder number three. Lobe 658 operates an intake valve of cylindernumber four and lobe 659 operates an exhaust valve of cylinder numberfour.

Camshaft saddle 602 includes valve bodies 670 a, 670 b, 670 c, and 670 dto support and provide oil passages leading to camshaft grooves. Inparticular, valve body 670 a includes inlet 613, first outlet 612, andsecond outlet 616. First outlet 612 provides oil to exhaust valveoperators. Second outlet 616 provides oil to intake valve operators.Valve body 670 b includes inlet 633, first outlet 636, and second outlet632. First outlet 636 provides oil to exhaust valve operators. Secondoutlet 632 provides oil to intake valve operators. Valve body 670 cincludes inlet 643, first outlet 646, and second outlet 642. Firstoutlet 646 provides oil to exhaust valve operators. Second outlet 642provides oil to intake valve operators. Valve body 670 d includes inlet653, first outlet 656, and second outlet 652. First outlet 656 providesoil to exhaust valve operators. Second outlet 652 provides oil to intakevalve operators. Passages 616, 632, 642, and 652 supply pressurize oilfrom oil pump 690 to intake valve operators 649 (shown in FIG. 6C) viagallery or passage 692 for respective cylinder numbers 1-4 when controlvalves 614, 634, 644, and 654 are activated and open. Outlets 612, 636,646, and 656 may supply oil pressure to exhaust valve operators 648(shown in FIG. 6C) when control valves 614, 634, 644, and 654 are open.Discontinuous grooves 608 a-608 d selectively provide an oil pathbetween inlets 613, 633, 643, and 653 and valve body outlets 612, 636,646, and 656 that lead to exhaust valve operators. Journals 605 a-605 dare partially circumscribed by discontinuous grooves 608 a-608 d.Accumulators 609 a-609 d provide oil to keep exhaust valves deactivatedwhen land 606 a covers passage 612 for short periods of time.

Referring now to FIG. 6B, a cross section valve body 670 a and itsassociated components is shown. Camshaft 420 is coupled to camshaftsaddle 602 via cap 699. Cap covers stationary groove 610 a formed incamshaft saddle 602. Camshaft 420 includes discontinuous groove 608 athat is axially aligned with stationary groove 610 a. Valve 614selectively allows oil to flow to intake valve operators via passage 616and into stationary groove 610 a. Land 606 a selectively covers anduncovers outlet 612 which provides oil to accumulator 609 a and exhaustvalve operators as camshaft 420 rotates.

Referring now to FIG. 6C, example deactivating intake valve operator 649and deactivating exhaust valve operator 648 for the hydraulicallyoperated valve deactivating system shown in FIG. 6A are shown. Camshaft420 rotates so that lobe 620 selectively lifts intake follower 645,which selectively opens and closes intake valve 52. Rocker shaft 644provides a selective mechanical linkage between intake follower 645 andintake valve contactor 647. The intake valve operator 649 and theexhaust valve operator 648 include the components and operate as theoperator described in FIG. 5C. Passage 646 allows pressurized oil toreach a piston shown in FIG. 5C so that intake valve 52 may bedeactivated (e.g., remain in a closed position during an engine cycle)Intake valve 52 may be activated (e.g., open and close during an enginecycle) when oil pressure in passage 646 is low.

Similarly, cam lobe 622 rotates to selectively lifts exhaust follower643, which selectively opens and closes exhaust valve 54. Rocker shaft642 provides a selective mechanical linkage between exhaust follower 643and exhaust valve contactor 640. Passage 641 allows oil to reach apiston shown in FIG. 5C so that exhaust valve 54 may be deactivated(e.g., remain in a closed position during an engine cycle). Low oilpressure in passage 641 activates (e.g., open and close during an enginecycle) exhaust valve 54 when piston 563 shown in FIG. 5C is returned toits normal or base position via spring 569.

In this way, a single cam may operate intake and exhaust valves.Further, the intake and exhaust valves that are driven via the singlecam may be deactivated via the intake and exhaust valve operators 648and 649.

Referring now to FIG. 6D, a valve and cylinder deactivation sequence forthe mechanism of FIGS. 6A-6C is shown. The valve deactivation sequencemay be provided by the system of FIGS. 1A and 6A-6C.

The first plot from the top of FIG. 6D is a plot of exhaust cam groovewidth at the passage leading to the exhaust valve operator versuscrankshaft angle. The vertical axis represents exhaust camshaft groovewidth and groove width increases in the direction of the vertical axisarrow. The horizontal axis represents engine crankshaft angle, wherezero is top-dead-center compression stroke for the cylinder whose intakeand exhaust grooves are shown. In this example, the exhaust groovecorresponds to the width of groove 608 a of FIG. 6A measured at the oiloutlet passage 612. The crankshaft angles for the exhaust groove widthare the same as the crankshaft angle in the third plot from the top ofFIG. 6D.

The second plot from the top of FIG. 6D is a plot of intake and exhaustvalve lift versus engine crankshaft angle. The vertical axis representsvalve lift and valve lift increases in the direction of the verticalaxis arrow. The horizontal axis represents engine crankshaft angle andthe three plots are aligned according to crankshaft angle. Thin solidline 690 represents intake valve lift for cylinder number one when itsintake valve operator is activated. Thick solid line 691 representsexhaust valve lift for cylinder number one when its exhaust valveoperator is activated. Thin dashed lines 692 represent intake valve liftfor cylinder number one if its intake valve operator were activated.Thin dashed line 693 represents exhaust valve lift for cylinder numberone if its exhaust valve operator were activated. Vertical lines A-Drepresent crankshaft angles of interest for the sequence.

The intake valve lift for cylinder number one is shown increasing andthen decreasing before crankshaft angle A. An oil control valve, such as614 of FIG. 6A, is closed before crankshaft angle A to prevent intakeand exhaust valve deactivation. The intake valve lift 690 is shownincreasing during cylinder number one's intake stroke before crankshaftangle A. Pressurized oil sufficient to deactivate intake valves is notpresent in the continuous intake camshaft groove before crankshaft angleA.

At crankshaft angle A, the oil control valve (e.g., 614 of FIG. 6A) maybe opened to deactivate intake and exhaust valves. The stationary groovewidth (e.g., 608 a of FIG. 6B) and passage 616 are pressurized with oilafter the oil control valve is opened so that the intake valve operatorlatching pin may be displaced while the outlet 616 is covered via land606 a. Thus, outlet passage 616 is not pressurized with oil at angle Abecause the land 606 a (shown in FIG. 6A) covers the valve body outlet616. Therefore, only the intake valve begins to be deactivated atcrankshaft angle A. The intake valve operator latching pin is disengagedfrom its normal position before crankshaft angle C to prevent the intakevalve from opening.

At crankshaft angle B, the land of the exhaust camshaft land 606 a forcylinder number one makes way for the discontinuous groove 608 a, whichallows oil to reach the outlet 616 and exhaust valve operator forcylinder number one. Oil can flow to the intake valve operator and theexhaust valve operator at crankshaft angle B, but since the exhaustvalve is partially lifted at crankshaft angle B, the exhaust valveoperates until the exhaust valve closes near crankshaft angle C. Theexhaust valve operator latching pin is disengaged from its normallyengaged position before crankshaft angle D to prevent the exhaust valvefrom opening.

At crankshaft angle C, the intake valve does not open since the intakevalve operator is deactivated for the engine cycle. Further, the exhaustvalve operator latching pin is disengaged from its normal positionbefore crankshaft angle D to prevent the exhaust valve from opening.Consequently, the exhaust valve does not open for the cylinder cycle.The intake and exhaust valves may remain deactivated until the intakeand exhaust operators are reactivated by reducing oil pressure to theintake and exhaust valve operators.

The intake and exhaust valve may be reactivated via deactivating the oilcontrol valve 614 and allowing oil pressure in the intake and exhaustvalve operators to be reduced or via dumping oil pressure from theintake and exhaust valve operators via a dump valve (not shown).

Oil accumulator 609 a maintains oil pressure in oil passage 616 duringthe portion of the cycle after crankshaft angle D when the exhaust camgroove land blocks passage 616. The accumulator 609 a compensates foroil leakage through various clearances during the time when oil supplyfrom the pump is interrupted. The oil accumulator 609 a may include adedicated piston and spring or may be combined with the latch pinmechanism such as the mechanism depicted in FIG. 5C.

Thus, the systems of FIGS. 1A-6D provide for a vehicle system,comprising: an engine; and a controller including non-transitoryexecutable instructions, which when executed by the controller, causethe controller to vary an actual total number of cylinders combustingair and fuel in the engine at an engine speed and load, varying whichcylinders combust air and fuel at the engine speed and load, and adjustspark timing of the engine in response to output of a first knock sensorwhen a cylinder is deactivated via ceasing fuel injection and not airflow to the cylinder, and further instructions to adjust spark timing ofthe engine in response to output of a second knock sensor when thecylinder is deactivated via ceasing fuel injection and air flow to thecylinder. The vehicle system includes where the first knock sensor andthe second knock sensor are selected based on output of an engine knocksensor to activated cylinder map. The vehicle system includes where thefirst knock sensor and the second knock sensor are selected based onoutput of an engine knock sensor to deactivated cylinder map.

In some examples, the vehicle system further comprises additionalinstructions to vary the actual total number of cylinders in response toan actual total number of engine revolutions. The vehicle system furthercomprises additional instructions to vary which cylinders combust airand fuel in response to an actual total number of engine revolutions.The vehicle system further comprises additional instructions to adjust aknock sensitivity threshold for a cylinder to a first level in responseto sensing knock via the first knock sensor, and additional instructionsto adjust the knock sensitivity threshold for the cylinder to a secondlevel in response to sensing knock via the second knock sensor.

It should be noted that the systems of FIGS. 1A-6D may be operated toprovide a desired engine torque where an actual total number of activecylinders may remain the same while the active cylinders that form theactual total number of active cylinders may change from engine cycle toengine cycle. In addition, the actual total number of cylinderscombusting air and fuel during an engine cycle to produce the desiredengine torque may change from engine cycle to engine cycle, if desired.This may be referred to as a rolling variable displacement engine. Forexample, a four cylinder engine having a firing order of 1-3-4-2 mayfire cylinders 1 and 3 during a first engine cycle, cylinders 3 and 2during a next engine cycle, cylinders 1-3-2 during a next engine cycle,cylinders 3-4-2 during a next engine cycle, and so on to provide aconstant desired engine torque.

Referring now to FIG. 7, a method for operating an engine withdeactivating cylinders and valves is shown. The method of FIG. 7 may beincluded in the system described in FIGS. 1A-6C. The method may beincluded as executable instructions stored in non-transitory memory. Themethod of FIG. 7 may perform in cooperation with system hardware andother methods described herein to transform an operating state of anengine or its components.

At 702, method 700 determines the engine hardware configuration. In oneexample, the engine hardware configuration may be stored in memory at atime of manufacture. The engine hardware configuration information mayinclude but is not limited to information describing a total actualnumber of engine cylinders, a total actual number of engine cylindersthat do not include deactivating intake and exhaust valves, an actualtotal number of engine cylinders that include deactivating exhaustvalves, an actual total number of engine cylinders that includedeactivating intake valves, identities (e.g., cylinder numbers) ofcylinders that include deactivating intake valves, identities ofcylinders that include deactivating exhaust valves, identities ofcylinders that do not include deactivating intake and exhaust valves,engine knock sensor locations, an actual total number of engine knocksensors, and other system configuration parameters. Method 700 reads thevehicle configuration information from memory and proceeds to 704.

At 704, method 700 judges if cylinder deactivation via deactivatingintake and/or exhaust valves is available given the system configurationinformation retrieved at 702. If method 700 judges that cylinderdeactivation is not available or possible via intake and/or exhaustvalves, the answer is no and method 700 proceeds to exit. Otherwise, theanswer is yes and method 700 proceeds to 706.

At 706, method 700 judges if only intake only cylinder deactivation isavailable. In other words, method 700 judges if only intake valves ofengine cylinders may be deactivated (e.g., held in a closed statethroughout an engine cycle) to deactivate cylinders while all exhaustvalves of all engine cylinders continue to operate as an engine rotates.In some engine configurations it may be desirable to deactivate onlyintake valves of cylinders being deactivated to reduce system cost.FIGS. 2B and 2C show two examples of such an engine configuration.Cylinder intake and exhaust valves may be deactivated in a closed statewhere they do not open from a closed position over an engine cycle.Method 700 may judge that only intake valves of engine cylinders may bedeactivated to deactivate engine cylinders while all engine exhaustvalves of engine cylinders continue to operate as the engine rotatesbased on the hardware configuration determined at 702. If method 700judges that only intake valves of engine cylinders may be deactivated todeactivate engine cylinders while all engine exhaust valves of enginecylinders continue to operate as the engine rotates, the answer is yesand method 700 proceeds to 708. Otherwise, the answer is no and method700 proceeds to 710.

At 708, method 700 determines engine cylinders in which intake valvesmay be deactivated and exhaust valves continue to operate as the enginerotates. Method may determine engine cylinders in which intake valvesmay be deactivated while exhaust valves continue to operate based on themethod of FIG. 8. Method 700 proceeds to 712 after engine cylinders inwhich intake valves may be deactivated are determined.

At 710, method 700 determines engine cylinders in which intake valvesand exhaust valves may be deactivated as the engine rotates. Method maydetermine engine cylinders in which intake and exhaust valves may bedeactivated based on the method of FIG. 10. Method 700 proceeds to 712after engine cylinders in which intake and exhaust valves may bedeactivated are determined.

At 712, method 700 determines the allowed or allowable cylinder modesfor operating the engine. A cylinder mode identifies how many enginecylinders are active and which cylinders are active (e.g., cylindernumber 1, 3, and 4). Method 700 determines the allowed cylinder modesaccording to the method of FIG. 11. Method 700 proceeds to 714 after theallowed cylinder modes are determined.

At 714, method 700 adjusts engine oil pressure responsive to cylindermodes. Method 700 adjusts engine oil pressure according to the method ofFIG. 31. Method 700 proceeds to 716 after engine oil pressure isadjusted.

At 716, method 700 deactivates selected cylinders according to theallowed cylinder modes. Method 700 deactivates intake and/or exhaustvalves to deactivate selected cylinders according to the allowedcylinder modes determined at 712. For example, if the engine is a fourcylinder engine and the allowed cylinder mode includes three activecylinders, method 700 deactivates one cylinder. The particular cylindersthat are active and the cylinders that are deactivated may be based oncylinder modes. The cylinder modes may change with vehicle operatingconditions so that a same actual total number of cylinders may be activeand a same actual total number of cylinders may be deactivated, but thecylinders that are activated and deactivated may change from cylindercycle to cylinder cycle. Valves operation of deactivated cylinders isbased on the cylinder deactivation mode associated with the deactivatedcylinder. For example, if the allowed cylinder modes include cylinderdeactivation modes from the method of FIG. 20, the valves in deactivatedcylinders may operate according to the cylinder deactivation modesdescribed in FIG. 20.

If a plurality of actual total numbers of active cylinders is allowed,the actual total number of active cylinders in a particular cylindermode that provides lowest fuel consumption while providing the desireddriver demand torque is activated. Further, the allowed transmissiongears that may be associated with the allowed cylinder mode that isactivated may be engaged.

Method 700 may deactivate intake and/or exhaust valves via the systemsdescribed herein or via other known valve deactivation systems. If anengine knock sensor or other sensor indicates engine noise greater thana threshold or vibration greater than a threshold immediately afterchanging cylinder modes, a different actual total number of activecylinders and transmission gear may be selected (e.g., the transmissiongear and cylinder mode prior to changing the cylinder mode, which may bea greater actual total number of active cylinders). The knock sensor maybe sampled at an engine crankshaft interval outside of an engine knockwindow to avoid switching modes based on knock. Knock sensor output fromwithin the knock window may be excluded for reactivating a cylinder inresponse to engine vibration.

Engine cylinders may be deactivated via holding intake valves in closedpositions over an entire engine cycle. Further, injection of fuel todeactivated cylinders may also be ceased. Spark delivery to deactivatedcylinders may also be ceased. In some examples, exhaust valves ofcylinders being deactivated are also held in closed positions over theentire engine cycle while the intake valves are deactivated so thatgases are trapped in the deactivated cylinders. Method 700 proceeds to718 after selected engine cylinders are deactivated via intake andexhaust valves.

At 718, method 700 controls engine knock responsive to cylinderdeactivation. Method 700 controls engine knock according to the methodof FIGS. 33-38. Method 700 proceeds to 720 after controlling engineknock.

At 720, method 700 performs cylinder deactivation diagnostics. Method700 performs cylinder diagnostics according to the method of FIGS.39-40. Method 700 proceeds to exit after performing cylinderdiagnostics.

Referring now to FIG. 8A, a method to determine cylinders in whichintake valves may be deactivated is shown. The method of FIG. 8 may beincluded in the system described in FIGS. 1A-6C. The method may beincluded as executable instructions stored in non-transitory memory. Themethod of FIG. 8 may perform in cooperation with system hardware andother methods described herein to transform an operating state of anengine or its components.

At 802, method 800 chooses an actual total number of cylinders for theengine. The actual total number of cylinders may be based on vehiclemass and performance requirements. In some examples, the engine willhave four cylinders while in other examples the engine will have six oreight cylinders. Further, the actual total number of engine cylinderswith valves that always remain active while the engine rotates isdetermined. In one example, the actual total number of cylinders thathave valves (e.g., intake and exhaust poppet valves) that remain activewhile the engine rotates is based on an amount of power the vehiclerequires to operate at a desired speed (e.g., 60 KPH). If the engine hasthe capacity to provide the amount of power with two or more cylinders,the engine may be produced with two cylinders that have valves thatalways remain active (e.g., opening and closing over an engine cycle).If the engine has the capacity to provide the amount of power with fouror more cylinders, the engine may be produced with four cylinders thathave valves that always remain active. The remaining cylinders areprovided with deactivating intake valves and non-deactivating exhaustvalves. Method 800 proceeds to 804 after the actual total number ofengine cylinders and the actual total number of cylinders with valvesthat always remain active are determined.

At 804, the engine is constructed with non-deactivating intake valveoperators and non-deactivating exhaust valve operators in enginecylinders that always remain active while the engine rotates. Theremaining engine cylinders are provided deactivating intake valveoperators and non-deactivating exhaust valve operators. Method 800proceeds to 806 after the engine is assembled with deactivating andnon-deactivating valves.

At 806, method 800 estimates an amount of oil in cylinders with intakevalves that are deactivated during an engine cycle so that the intakevalves do not open during an engine cycle or a cycle of the cylinder inwhich the intake valves operate. In one example, the amount of oil inengine cylinders is estimated based on the empirical model described inFIG. 8B. Method 800 determines amounts of oil in each engine cylinderwhere intake valves of the cylinder are deactivated and where thecylinder is deactivated such that air flow through the cylinder issubstantially ceased (e.g., less than 10% of the air flow through thecylinder at idle conditions). The amount of oil in each cylinder isrevised each engine cycle. Method 800 proceeds to 808 after the oilamount in each cylinder is determined.

Additionally, method 800 may estimate engine oil quality at 806. Engineoil quality may be an estimate of contaminants in the engine oil. Theengine oil quality may be assigned a value from 0 to 100, zerocorresponding to oil at an end of its life cycle and one hundredcorresponding to fresh oil. In one example, the estimate of engine oilquality is based on engine operating time, engine load during theoperating time, and engine speed during the operating time. For example,average engine load and speed may be determined over the engineoperating time. The average engine load and speed index a table ofempirically determined values and the table outputs an oil qualityvalue. It may be desirable to limit an amount of time cylinderdeactivation is available in response to oil quality because low oilquality may increase engine wear during cylinder deactivation and/orincrease engine emissions during cylinder deactivation.

Method 800 may also determine an actual total number of particulateregenerations since a last time engine oil was changed. A particulatefilter may be regenerated via raising particulate filter temperature andcombusting carbonaceous soot stored in the particulate filter. Each timethe particulate filter is regenerated after an engine oil change, anactual total number of particulate filter regenerations is increased.

At 808, method 800 prevents cylinders containing more than a thresholdamount of oil from being deactivated. In other words, if a cylinder withdeactivated intake valves (e.g., intake valves that remain closed overan engine cycle) contains more than a threshold amount of oil, thecylinder is reactivated (e.g., cylinder intake and exhaust valves openand close during an engine cycle and air and fuel are combusted in thecylinder) so that oil entry into the cylinder may be limited. Thecylinder is reactivated via activating the intake valve operator andsupplying spark and fuel to the cylinder. If the cylinder isreactivated, it remains activated at least until an amount of oil in thecylinder is less than a threshold amount. Further, the amount of intakevalve and exhaust valve opening time overlap may be increased inresponse to the amount of oil in the deactivated cylinder exceeding athreshold. By increasing intake valve and exhaust open time overlap inresponse to the amount of oil in a cylinder exceeding a threshold, itmay be possible to evacuate oil vapors from the cylinder to improvesubsequent combustion event stability and emissions. Further, onecylinder may be activated in response to an amount of oil in the onecylinder, while during a same engine cycle, a second cylinder may bedeactivated so that a total actual number of active engine cylindersremains constant during an engine cycle. The cylinders may be activatedand deactivated as described elsewhere herein. For example, the onecylinder may be activated via opening intake and exhaust valves during acycle of the one cylinder. The second cylinder may be deactivated viaclosing and holding closed intake, or intake and exhaust valves, closedduring a cycle of the second cylinder.

If a cylinder with deactivating intake valves and non-deactivatingexhaust valves is deactivated by holding intake valves of thedeactivated cylinder closed during a cycle of the deactivated cylinder,while exhaust valves continue to open and close, closing timing ofexhaust valves may be adjusted in response to deactivating the cylinderso that cylinder compression and expansion losses may be reduced. Method800 proceeds to exit after cylinders containing more than a thresholdamount of oil are reactivated.

Additionally at 808, cylinders may not be deactivated or may bereactivated (e.g., combusting air and fuel in the cylinders) in responseto oil quality being less than a threshold value. Further, method 800may activate engine cylinders or prevent engine cylinders from beingdeactivated in response to an actual total number of particulate filterregenerations since a last engine oil change being greater than athreshold. These actions may improve vehicle emissions and/or reduceengine wear.

Referring now to FIG. 8B, a block diagram of an example empirical modelfor estimating an amount of oil in an engine cylinder is shown. Anamount of oil in each deactivated cylinder may be estimated via a modelsimilar to model 850, although variables in the described functions ortables may have different values depending on the cylinder number.

Model 850 estimates a base oil amount that enters into cylinders thathave deactivated intake valves (e.g., intake valves that remain in aclosed position over an engine or cylinder cycle) and operating exhaustvalves at block 852. The cylinder oil amounts are empirically determinedand installed into a table or function that is stored in controllermemory. In one example, the table or function is indexed by engine speedand in cylinder or exhaust pressure. The table or function outputs anamount of oil in the cylinder. The amount of oil is directed to block854.

At block 854, the amount of oil in a cylinder is multiplied by a scalaror real number that adjusts the amount of oil in response to oiltemperature. Oil viscosity may vary with oil temperature and the amountof oil that may enter a deactivated cylinder may vary with oiltemperature. Since oil viscosity can decrease with oil temperature, theamount of oil that may enter a deactivated cylinder may increase withincreased oil temperature. In one example, block 854 includes aplurality of empirically determined scalars for different oiltemperatures. The amount of oil from block 852 is multiplied by thescalar in block 854 to determine the amount of oil in the enginecylinder as a function of oil temperature.

At 856, a scalar based on engine or cylinder compression ratio (CR) ismultiplied by the output of block 854 to determine the amount of oil inthe engine cylinder as a function of oil temperature and enginecompression ratio. In one example, the amount of oil in the cylinder isincreased for higher cylinder compression ratios since a vacuum iscreated in the cylinder after the exhaust valve closes. The value of 856is empirically determined and stored to memory.

At 858, the amount of oil in the cylinder is multiplied by a value thatis a function of exhaust valve closing position or trapped cylindervolume. The value decreases as exhaust valve closing timing is retardedfrom top-dead-center exhaust stroke since additional volume of exhaustgas is trapped in the cylinder as exhaust valve closing retardincreases. The value decreases as exhaust valve closing timing isadvanced from top-dead-center exhaust stroke since additional volume ofexhaust gas is trapped in the cylinder as exhaust valve closing advanceincreases. The function of 858 is empirically determined and stored tomemory. The amount oil in the cylinder is passed to block 860.

At block 860, the amount of oil in a cylinder is multiplied by a scalarthat adjusts the amount of oil in response to engine temperature. Enginetemperature may affect clearances between engine components and theamount of oil that enters the cylinder may vary with engine temperatureand engine component clearances. In one example, block 860 includes aplurality of empirically determined scalars for different enginetemperatures. The amount of oil that enters the cylinder decreases asengine temperature increases since clearance between engine componentsmay decrease with increasing engine temperature. Block 860 outputs anestimate of oil in an engine cylinder.

Referring now to FIG. 9, an example operating sequence for a fourcylinder engine is shown. In this example, engine cylinder numbers twoand three may be selectively activated and deactivated via activatingand deactivating intake valves of cylinder numbers two and three. Thefour cylinder engine has a 1-3-4-2 firing order when it combusts air andfuel. The vertical markers at time T0-T7 represent times of interest inthe sequence. The plots of FIG. 9 are time aligned and occur at the sametime.

The first plot from the top of FIG. 9 is a plot of estimated oil incylinder number two versus time. The vertical axis represents anestimated amount of oil in cylinder number two and the estimated amountof oil in cylinder number two increases in the direction of the verticalaxis arrow. The horizontal axis represents time and time increases fromthe left side of the plot to the right side of the plot. Horizontal line902 represents a threshold limit for an amount of oil in cylinder numbertwo which is not to be exceeded.

The second plot from the top of FIG. 9 is a plot of estimated oil incylinder number three versus time. The vertical axis represents anestimated amount of oil in cylinder number three and the estimatedamount of oil in cylinder number three increases in the direction of thevertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the plot to the right side of the plot.Horizontal line 904 represents a threshold limit for an amount of oil incylinder number three which is not to be exceeded.

The third plot from the top of FIG. 9 is a plot of the number ofrequested operating cylinders. The number of requested operatingcylinders may be a function of driver torque demand, engine speed, andother operating conditions. The vertical axis represents the requestednumber of operating engine cylinders and the requested number ofoperating engine cylinders are shown along the vertical axis. Thehorizontal axis represents time and time increases from the left side ofthe plot to the right side of the plot.

The fourth plot from the top of FIG. 9 is a plot of the operating stateof cylinder number two versus time. The vertical axis representscylinder number two operating state. Cylinder number two is operatingcombusting air and fuel with intake and exhaust valves opening andclosing during an engine cycle when the trace is at a higher level nearthe vertical axis arrow. Cylinder number two is not operating and notcombusting air and fuel when the trace is at a lower level near thehorizontal axis. The intake valves are closed for the entire enginecycle when the trace is near the horizontal axis and exhaust valves openand close during an engine cycle when the trace is at the lower levelnear the horizontal axis arrow.

The fifth plot from the top of FIG. 9 is a plot of the operating stateof cylinder number three versus time. The vertical axis representscylinder number three operating state. Cylinder number three isoperating combusting air and fuel with intake and exhaust valves openingand closing during an engine cycle when the trace is at a higher levelnear the vertical axis arrow. Cylinder number three is not operating andnot combusting air and fuel when the trace is at a lower level near thehorizontal axis. The intake valves are closed for the entire enginecycle when the trace is near the horizontal axis and exhaust valves openand close during an engine cycle when the trace is at the lower levelnear the horizontal axis arrow.

At time T0, the estimated amount of oil in cylinder number two is low.The estimated amount of oil in cylinder number three is also low. Theengine is operating with four active (e.g., cylinders combusting air andfuel) cylinders as indicated by the requested number of cylinders beingequal to four and the operating states of cylinder number two and numberthree being active (e.g., cylinder operating state traces are at higherlevels). Cylinder numbers one and four are active whenever the engine ismiming and combusting air and fuel.

At time T1, the estimated amounts of oil in cylinder numbers two andthree is low. The number of requested operating cylinders is reducedfrom four to three. The requested number of engine cylinders may bereduced in response to a lower driver demand torque. Cylinder numberthree is deactivated (e.g., combustion is stopped in cylinder numberthree, intake valves of cylinder number three are deactivated such thatthey do not open and close during an engine cycle, fuel delivery to thecylinder ceases, spark delivery to the cylinder may be ceased, andexhaust valves of cylinder number three continue to open and closeduring each engine cycle) in response to the requested number ofcylinders being three. Cylinder number two continues to operate withactive intake valves and combustion.

Between time T1 and time T2, the estimated amount of oil in cylindernumber two remains low and constant. The estimated amount of oil incylinder number three is increasing. The amount of oil in cylindernumber three increases because a vacuum may form in cylinder numberthree after exhaust valves of cylinder number three close because intakevalves of cylinder number three are deactivated.

At time T2, the amount of oil in cylinder number three equals or exceedsthreshold 904. Therefore, cylinder number three is reactivated whichincreases pressure in the cylinder and pushes oil out of the cylinderpast the cylinder rings, thereby reducing the amount of oil in cylindernumber three. However, since the requested number of cylinders is three,cylinder number two is deactivated (e.g., combustion is stopped incylinder number two, intake valves of cylinder number two aredeactivated such that they do not open and close during an engine cycle,fuel delivery to the cylinder ceases, spark delivery to the cylinder maybe ceased, and exhaust valves of cylinder number two open and closeduring each engine cycle). In this way, the requested number ofoperating cylinders is provided even when the oil amount of one cylinderis at or above a threshold limit. The estimated amount of oil incylinder number two is at a lower level. The operating state of cylindernumber two is low to indicate cylinder number two is deactivated. Theoperating state of cylinder number three is high to indicate cylindernumber three is activated.

At time T3, the number of requested operating cylinders is two and theestimated amount of oil in cylinder number three is low. Cylinder numberthree is deactivated in response to the low amount of oil in cylindernumber three and the number of requested operating cylinders. Cylindernumber two remains in a deactivated state. The amount of oil in cylindernumber two continues to increase.

At time T4, the amount of oil in cylinder number two exceeds thresholdlevel 902 and the number of requested operating cylinders is two.Cylinder number two is reactivated to evacuate oil from cylinder numbertwo. Cylinder number three remains deactivated so that the number ofcylinders combusting is near the requested number of operatingcylinders. A short time after time T4, cylinder number two isreactivated in response to the estimated amount of oil in cylindernumber two being low.

At time T5, the amount of oil in cylinder number three exceeds thresholdlevel 904 and the number of requested operating cylinders is two.Cylinder number three is reactivated to evacuate oil from cylindernumber three. Cylinder number two remains deactivated so that the numberof cylinders combusting is near the requested number of operatingcylinders. A short time after time T5, cylinder number three isreactivated in response to the estimated amount of oil in cylindernumber three being low.

At time T6, the amount of oil in cylinder number two exceeds thresholdlevel 902 and the number of requested operating cylinders is two.Cylinder number two is reactivated to evacuate oil from cylinder numbertwo. Cylinder number three remains deactivated so that the number ofcylinders combusting is near the requested number of operatingcylinders. A short time after time T6, cylinder number two isreactivated in response to the estimated amount of oil in cylindernumber two being low.

At time T7, the requested number of operating cylinders is increased inresponse to an increase in driver demand torque. The operating states ofcylinder numbers two and three changes to active to indicate cylindernumbers two and three have been reactivated in response to the number ofoperating cylinders. The estimated amount of oil in cylinder numbers twoand three is reduced by activating cylinder numbers two and three.

In this way, engine cylinders may be selectively deactivate andactivated to conserve fuel and reduce oil in engine cylinders. Further,the activated cylinders may be deactivated to reduce oil in enginecylinders and to attempt to match the requested number of operatingcylinders. Activating cylinders to remove oil from cylinders haspriority over deactivating cylinders to match the requested number ofoperating cylinders so that oil consumption may be reduced.

Referring now to FIG. 10, a method to determine cylinders in whichintake valves may be deactivated is shown. The method of FIG. 10 may beincluded in the system described in FIGS. 1A-6C. The method may beincluded as executable instructions stored in non-transitory memory. Themethod of FIG. 10 may perform in cooperation with system hardware andother methods described herein to transform an operating state of anengine or its components.

At 1002, method 1000 an actual total number of cylinders for the engineis chosen. The actual total number of cylinders may be based on vehiclemass and performance requirements. In some examples, the engine willhave four cylinders while in other examples the engine will have six oreight cylinders. Further, the actual total number of engine cylinderswith valves that always remain active while the engine rotates isdetermined. In one example, the actual total number of cylinders thathave valves (e.g., intake and exhaust poppet valves) that remain activewhile the engine rotates is based on an amount of power the vehiclerequires to operate at a desired speed (e.g., 60 KPH). If the engine hasthe capacity to provide the amount of power with four or more cylinders,the engine may be produced with four cylinders that have valves thatalways remain active (e.g., opening and closing over an engine cycle).If the engine has the capacity to provide the amount of power with sixor more cylinders, the engine may be produced with six cylinders thathave valves that always remain active. The remaining cylinders areprovided with deactivating intake valves and non-deactivating exhaustvalves. Method 1000 proceeds to 1004 after the actual total number ofengine cylinders and the actual total number of cylinders with valvesthat always remain active are determined.

At 1004, the engine is constructed with non-deactivating intake valveoperators and non-deactivating exhaust valve operators in enginecylinders that always remain active while the engine rotates. Theremaining engine cylinders are provided deactivating intake valveoperators and deactivating exhaust valve operators. Method 1000 proceedsto 1006 after the engine is assembled with deactivating andnon-deactivating valves.

At 1006, method 1000 estimates an amount of oil in cylinders with intakevalves that are deactivated during an engine cycle so that the intakevalves do not open during an engine cycle or a cycle of the cylinder inwhich the intake valves operate. In one example, the amount of oil inengine cylinders is estimated based on the empirical model described inFIG. 8B; however, the functions and/or tables described in FIG. 8B mayinclude different variable values than those for an engine withcylinders that are deactivated via closing only intake valves over anengine cycle. Method 1000 determines amounts of oil in each enginecylinder where intake valves of the cylinder are deactivated and wherethe cylinder is deactivated such that air flow through the cylinder issubstantially ceased (e.g., less than 10% of the air flow through thecylinder at idle conditions). The amount of oil in each cylinder isrevised each engine cycle. Method 1000 proceeds to 1008 after the oilamount in each cylinder is determined.

At 1008, method 1000 prevents cylinders containing more than a thresholdamount of oil from being deactivated. In other words, if a cylinder withdeactivated intake and exhaust valves (e.g., intake and exhaust valvesthat remain closed over an engine cycle) contains more than a thresholdamount of oil, the cylinder is reactivated (e.g., cylinder intake andexhaust valves open and close during an engine cycle and air and fuelare combusted in the cylinder) so that oil entry into the cylinder maybe limited. The cylinder is reactivated via activating the intake valveoperator and supplying spark and fuel to the cylinder. Method 1000proceeds to exit after cylinders containing more than a threshold amountof oil are reactivated.

Referring now to FIG. 11, a method to determine available cylinder modesfor an engine is shown. The method of FIG. 11 may be included in thesystem described in FIGS. 1A-6C. The method may be included asexecutable instructions stored in non-transitory memory. The method ofFIG. 11 may perform in cooperation with system hardware and othermethods described herein to transform an operating state of an engine orits components.

At 1102, method 1100 evaluates engine cylinder mode busyness againstlimits to determine if changing of cylinder modes is too busy or if itis reasonable. If the cylinder mode is switched too often, the vehicle'soccupants may be made aware of cylinder mode shifting such that cylindermode shifting becomes undesirable. Method 1100 evaluates cylinder modeshifting according to the method of FIG. 12 and proceeds to 1106.

At 1106, method 1100 evaluates which cylinder modes may provide arequested amount of engine brake torque. Method 1100 proceeds to themethod of FIG. 14 to determine which cylinder modes may provide therequested amount of engine brake torque. Method 1100 proceeds to 1108after determining which cylinder modes may provide the requested amountof brake torque.

At 1108, method 1100 evaluates if changing cylinder mode will reducefuel consumption. Method 11 proceeds to the method of FIG. 15 todetermine if changing the cylinder mode may conserve fuel. Method 1100proceeds to 1112 after it is determined if changing cylinder mode willconserve fuel.

At 1112, method 1100 evaluates a cam phasing rate for determining thecylinder mode. The cam phasing rate is a rate that a cam torque actuatedphasor changes a position of an engine's cam relative to a position ofthe engine's crankshaft. Because cam torque actuated variable valvetiming phase actuators rely on valve spring force to operate, andbecause deactivating a cylinders valves reduces the reaction forceprovided by the valve springs, it may not be desirable to use somecylinder modes when high rates of change of cam phase is desired. Method1100 evaluates the cam phase rate for available cylinder modes accordingto the method of FIG. 16 and then proceeds to 1114.

At 1114, method 1100 evaluates different transmission gears forselecting the cylinder mode. Method 1100 evaluates differenttransmission gears for selecting the cylinder mode according to themethod of FIG. 18. Method 1100 proceeds to 1116 after evaluatingdifferent transmission gears for selecting the cylinder mode.

At 1116, method 1100 evaluates towing and hauling modes for selectingthe cylinder mode. Method 1100 evaluates towing and hauling modes forselecting the cylinder mode according to the method of FIG. 20. Method1100 proceeds to 1118 after evaluating towing and hauling modes forselecting the cylinder mode.

At 1118, method 1100 judges if select conditions are present forselecting the cylinder mode. Method 1100 determines of conditions arepresent for determining the cylinder mode according to the method ofFIG. 22. Method 1100 proceeds to 1120 after determining if conditionsare present for selecting the cylinder mode.

At 1120, method 1100 controls engine manifold absolute pressure (MAP)during conditions when one or more cylinders are being deactivated viadeactivating intake and/or exhaust valves of engine cylinders. Further,fuel delivery to the cylinder and spark delivery to the cylinder areceased when the cylinder is deactivated. Method 1100 controls MAPaccording to the method of FIG. 23 and proceeds to 1121.

At 1121, method 1100 controls engine manifold absolute pressure (MAP)during conditions when one or more cylinders are being activated viaactivating intake and/or exhaust valves of engine cylinders. Further,fuel delivery to the cylinder and spark delivery to the cylinder areactivated when the cylinder is activated. Method 1100 controls MAPaccording to the method of FIG. 25 and proceeds to 1122.

At 1122, method 1100 controls engine torque during changing cylindermodes. Method 1100 controls engine torque according to the method ofFIG. 27A before proceeding to 1124.

At 1124, method 1100 controls fuel supplied to the engine for changingcylinder modes. Method 1100 controls fuel supplied to the engineaccording to the method of FIG. 29. Method 1100 proceeds to exit aftercontrolling fuel flow to the engine.

Referring now to FIG. 12, a method for evaluating whether or notchanging the cylinder mode exceeds busyness limits is shown. The methodof FIG. 12 may be included in the system described in FIGS. 1A-6C. Themethod of FIG. 12 may be included as executable instructions stored innon-transitory memory. The method of FIG. 12 may perform in cooperationwith system hardware and other methods described herein to transform anoperating state of an engine or its components.

At 1202, method 1200 judges if the present execution of method 1200 is afirst execution of method 1200 since the vehicle and engine were stoppedand shutdown. Method 1200 may judge that the present execution of method1200 is a first execution since the vehicle was activated after thevehicle was deactivated (e.g., stopped without intent to restartimmediately). In one example, method 1200 judges that the presentexecution is a first execution when a value in memory is zero and themethod has not been executed since a driver requested the vehicle tostart via a pushbutton or key. If method 1200 judges that the presentexecution of method 1200 is a first execution of method 1200 since theengine was stopped, the answer is yes and method 1200 proceeds to 1220.Otherwise, the answer is no and method 1200 proceeds to 1204.

At 1220, method 1200 determines values of variables PAYBACK_TIME andVDE_BUSY. The variable PAYBACK_TIME is an amount of time it takes in anewly selected cylinder mode or variable displacement engine (VDE) modeto cover the fuel cost of transitioning from one cylinder mode or VDEmode to the next cylinder mode or VDE mode. The fuel cost may be due toreducing engine torque via spark retard or some other adjustment tocontrol engine torque during mode transitions. The variable VDE_BUSY isa value that is a basis for determining whether or not cylinder mode orVDE switching is occurring at a higher than desired frequency. The valueis updated based on the number of cylinder mode or VDE transitions andthe amount of time spent in a cylinder mode or VDE mode. VDE_BUSY isinitially set to zero and PAYBACK_TIME is empirically determined andstored in memory. In one example, the variable PAYBACK_TIME may varydepending on the cylinder mode being exited and the cylinder mode beingentered. There may be VDE_BUSY variables for each cylinder mode as shownin FIG. 13. Method 1200 proceeds to 1204 after the variable values aredetermined.

At 1204, method 1200 judges if the engine is exiting a valvedeactivation mode. Method 1200 may judge that the engine is exiting avalve deactivation mode if valves of one or more cylinders are beingactivated (e.g., intake valves transition from not opening and closingduring an engine cycle to opening and closing during an engine cycle) inan engine cycle. If method 1200 judges that the engine is exiting avalve deactivation mode and valves of at least one cylinder are beingreactivated during an engine cycle, the answer is yes and method 1200proceeds to 1208. Otherwise, the answer is no and method 1200 proceedsto 1230.

At 1230, method 1200 judges if the engine is operating in a valvedeactivation mode. Method 1200 may judge that the engine is operating ina valve deactivation mode if intake and/or exhaust valves of an enginecylinder stay closed and do not open and close during an engine cycle.If method 1200 judges that the engine is operating in a valvedeactivation mode, the answer is yes and method 1200 proceeds to 1232.Otherwise, the answer is no and method 1200 proceeds to 1210.

At 1232, method 1200 counts an amount of time one or more cylinders havevalves in a deactivated state to determine an amount of time the engineis in a deactivation mode. The engine may have more than onedeactivation mode and time in each deactivation mode may be determined.For example, an eight cylinder engine may deactivate two cylinders orfour cylinders to provide two deactivation modes. The first deactivationmode is where two cylinders are deactivated and the second deactivationmode is where four cylinders are deactivated. Method 1200 determines theamount of time the engine has two deactivated cylinders and the amountof time the engine has four deactivated cylinders. Method 1200 proceedsto 1210 after determining an amount of time one or more engine cylindersare in a deactivation mode.

At 1208, method 1200 determines an amount of time to add or subtractfrom the VDE_BUSY variable based on an amount of time one or modecylinders have deactivated valves and the PAYBACK_TIME. A larger numberis added to the VDE_BUSY variable if the engine has deactivatedcylinders in a mode for a short period of time relative to thePAYBACK_TIME. For example, when an eight cylinder engine operates withactive valves in four cylinders for four seconds method 1200 may add avalue of 120 to the VDE_BUSY variable when the variable PAYBACK_TIME is20. On the other hand, when an eight cylinder engine operates withactive valves in four cylinders for 19 seconds method 1200 may add avalue of 40 to the VDE_BUSY variable when the variable PAYBACK_TIME is20. If the eight cylinder engine operates with active valves in fourcylinders for 45 seconds method 1200 may add a value of −10 to theVDE_BUSY variable when the variable PAYBACK_TIME is 20. The value addedto VDE_BUSY may be a linear or non-linear function of the differencebetween the amount of time the engine spends in the cylinderdeactivation mode and the value of PAYBACK_TIME. Method 1200 proceeds to1210 after the value of VDE_BUSY has been adjusted.

At 1210, method 1200 subtracts a predetermined amount or value from theVDE_BUSY variable. For example, method 1210 may subtract a value of 5from the VDE_BUSY variable. By subtracting a predetermined amount fromthe VDE_BUSY variable, the VDE_BUSY variable may be driven toward avalue of zero. The variable VDE_BUSY is limited to positive valuesgreater than zero. Method 1200 proceeds to 1212 after subtracting thepredetermined amount from the VDE_BUSY variable.

At 1212, method 1200 judges if cylinder valve deactivation is requestedto lower the number of active cylinders. Cylinder valves deactivationmay be requested in response to a lower driver demand torque or otherdriving conditions. If method 1200 judges that cylinder valvedeactivation is requested from the present cylinder mode or VDE mode,the answer is yes and method 1200 proceeds to 1214. Otherwise, theanswer is no and method 1200 proceeds to 1240.

At 1240, method 1200 judges if cylinder valve reactivation is requestedto increase the number of active cylinders (e.g., if intake valves oftwo cylinders are requested to be reactivated in response to an increasein driver demand torque). Cylinder valves may be reactivated toreactivate a cylinder. The cylinder may be reactivated in response to anincrease in driver demand torque or another condition. If method 1200judges that cylinder valve reactivation is requested, the answer is yesand method 1200 proceeds to 1244. Otherwise, the answer is no and method1200 proceeds to 1242.

At 1244, method 1200 authorizes reactivation of deactivated cylindervalves and cylinders. The cylinder valves may be reactivated via themechanisms shown in FIGS. 6A and 6B or other known mechanisms Method1200 proceeds to exit after authorizing reactivation of deactivatedcylinder valves. The valves may be activated according to the method ofFIG. 22.

At 1242, method 1200 does not authorize activating or deactivating adifferent number of cylinder valves than those that are presentlyactivated or deactivated. In other words, the number of activated valvesand cylinders is maintained at its present value. Method 1200 proceedsto exit after maintaining the present number of activated anddeactivated cylinders.

At 1214, method 1200 judges if an amount of time since a cylinder valvereactivation request is greater than the value of variable VDE_BUSY. Ifso, the answer is yes and method 1200 proceeds to 1216. Otherwise, theanswer is no and method 1200 proceed to 1242. In this way, cylindervalve deactivation may be delayed until an amount of time betweencylinder mode or VDE mode changes is greater than the value of VDE_BUSYwhich increases when the frequency of cylinder valve deactivationincreases and decreases when the frequency of cylinder valvedeactivation decreases.

At 1216, method 1200 authorizes deactivation of selected cylinder valvesto deactivate selected cylinders. Deactivation of fuel supplied to thecylinders and spark to the cylinders may also be authorized. The valvesmay be deactivated according to the method of FIG. 22.

Referring now to FIG. 13, an engine operating sequence according to themethod of FIG. 12 is shown. The vertical lines at time T1300-T1314represent times of interest in the sequence. FIG. 13 shows six plots andthe plots are time aligned and occur at the same time. In this example,deactivating a cylinder means deactivating at least intake valves of thecylinder being deactivated so that the deactivated intake valves remainin closed states during an entire engine cycle. In some examples,exhaust valves of deactivated cylinders are also deactivated so that theexhaust valves remain in a closed state during a cycle of the engine.Spark and fuel are not supplied to deactivated cylinders so thatcombustion does not occur in deactivated cylinders. Alternatively,cylinder deactivation may include ceasing combustion and fuel injectedto a cylinder while valves of the cylinder continue to operate.

The first plot from the top of FIG. 13 is a plot of cylinderdeactivation request versus time. Engine cylinders may be deactivated inresponse to the cylinder deactivation request. The vertical axisrepresents cylinder deactivation request and the horizontal axisrepresents time. Time increases from the left side of the figure to theright side of the figure. In this example, the engine is an eightcylinder engine that may operate with four, six, or eight activecylinders. The numbers along the vertical axis identify which cylindersare requested or not requested to be deactivated. For example, when thetrace is at the level of eight, no cylinders are requested deactivated.When the trace is at the level of six, two cylinders are requesteddeactivated. Four cylinders are requested deactivated when the trace isat the level of four. A cylinder deactivation request may be based ondriver demand torque or other vehicle conditions. In some examples, onlyintake valves of a cylinder are deactivated to deactivate a cylinder. Inother examples, intake valves and exhaust valves are deactivated todeactivate a cylinder. If a cylinder is deactivated, spark and fuel flowcease to the cylinder.

The second plot from the top of FIG. 13 is a plot of cylinder activationstate versus time. The cylinder activation state provides the actualoperating state of engine cylinders. The vertical axis representscylinder activation state and the horizontal axis represents time. Thenumbers along the vertical axis identify which cylinders are activated.For example, when the trace is at the level of eight, all cylinders areactivated. If the trace is at the level of six, six cylinders areactivated. Four cylinders are activated when the trace is at the levelof four. The horizontal axis represents time and time increases from theleft side of the figure to the right side of the figure.

The third plot from the top of FIG. 13 is a plot of the amount of timethe engine is in the first cylinder mode, six cylinder operation in thisexample. The vertical axis represents the amount of time in the firstcylinder mode and time in the first cylinder mode increases in thedirection of the vertical axis arrow. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

The fourth plot from the top of FIG. 13 is a plot of the amount of timethe engine is in the second cylinder mode, four cylinder operation inthis example. The vertical axis represents the amount of time in thesecond cylinder mode and time in the second cylinder mode increases inthe direction of the vertical axis arrow. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

The fifth plot from the top of FIG. 13 is a plot of the value of theVDE_BUSY variable for the first cylinder valve deactivation mode, sixcylinder operation in this example. The vertical axis represents thevalue of the VDE_BUSY variable in the first cylinder mode. The valuecorresponds to an amount of time that has to pass after a request toenter the first cylinder mode is requested before the first cylindermode may be entered. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

The sixth plot from the top of FIG. 13 is a plot of the value of theVDE_BUSY variable for the second cylinder mode, four cylinder operationin this example. The vertical axis represents the value of the VDE_BUSYvariable in the second cylinder mode. The value corresponds to an amountof time that has to pass after a request to enter the second cylindermode is requested before the second cylinder mode may be entered. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure.

At time T1300, the engine is operating with all valves and cylindersactive as indicated by the cylinder activation state being a value ofeight. The cylinder deactivation request is not requesting to deactivateany valves or cylinders and the amount of time in the first and secondcylinder modes is zero. The VDE_BUSY variable for the first cylindermode, which deactivates cylinders, is zero. The VDE_BUSY variable forthe second cylinder mode, which deactivates cylinders, is also zero.

At time T1301, the cylinder deactivation request changes state torequest deactivation of valves of two cylinders so that the eightcylinder engine operates with six active cylinders. The cylinderactivation state changes state to indicate that the engine is operatingwith six active cylinders and with valves of two cylinders deactivated.Time begins to accumulate in the first cylinder mode because the engineis in the first cylinder mode (e.g., operating with six activecylinders). No time accumulates in the second cylinder mode because theengine is not operating in the second cylinder mode (e.g., operatingwith four active cylinders). The variables VDE_BUSY for the firstcylinder mode and VDE_BUSY for the second cylinder mode are zero sincethe engine has not exited the first or second cylinder modes.

At time T1302, the cylinder deactivation request change state to requestdeactivation of no cylinder valves so that the engine operates as aneight cylinder engine. The cylinder activation state changes state toindicate that the engine is operating with eight active cylinders andwith no deactivated valves. Accumulation of time in the first cylindermode ceases because the engine is operating all cylinder valves and asan eight cylinder engine. No time accumulates in the second cylindermode because the engine is not operating in the second cylinder mode.The value of VDE_BUSY for the first cylinder mode increases based on thetime duration the engine was in the first cylinder mode.

At time T1303, the cylinder deactivation request again changes state torequest deactivation of valves of two cylinders so that the eightcylinder engine operates with six active cylinders. The cylinderactivation state does not change state because the value of VDE_BUSY forthe first cylinder mode is greater than the variable PAYBACK_TIME (notshown). The value of VDE_BUSY for the first cylinder mode decreases as apredetermined amount of time is subtracted from VDE_BUSY first cylindermode each time the method is executed. No time accumulates in the secondcylinder mode because the engine is not operating in the second cylindermode (e.g., operating with four active cylinders). VDE_BUSY for thesecond cylinder mode is zero since the engine has not exited the secondcylinder mode.

At time T1304, the value of VDE_BUSY for the first cylinder mode isequal to or less than the value of the variable PAYBACK_TIME so cylindervalves are deactivated to provide six cylinder engine operation asindicated by the cylinder activation state transitioning to the levelthat indicates six cylinder engine operation. The amount of time in thefirst cylinder mode begins to increase. The amount of time in the secondcylinder mode remains at zero. The value of VDE_BUSY for the firstcylinder valve deactivation mode continues to decrease and the value ofVDE_BUSY for the second cylinder valve deactivation mode remains atzero.

At time T1305, the cylinder deactivation request transitions back to thevalue of eight. The cylinder activation state also transitions back to avalue of eight based on the cylinder deactivation request. The amount oftime in the first cylinder mode is small so the value of VDE_BUSY forthe first cylinder mode is increased by a large amount. The value ofVDE_BUSY for the second cylinder mode is zero because the engine was notin the second cylinder mode. Shortly thereafter, the cylinderdeactivation request transitions to a value of six to requestdeactivation of valves in two engine cylinders so that the engineoperates as a six cylinder engine combusting air fuel mixtures in six ofeight cylinders. However, the engine is not switched into six cylinderoperation as indicated by the cylinder activation state remaining at avalue of eight. The engine does not switch into six cylinder mode anddeactivate valves of two cylinders because the value of VDE_BUSY for thefirst cylinder mode is greater than the value of the variablePAYBACK_TIME (not shown).

At time T1306, the engine transitions to six cylinder mode wherecylinder valves in two engine cylinders are deactivated to deactivatetwo cylinders. Fuel and spark are not provided to the two deactivatedcylinders. The cylinder activation state transitions to a value of sixto indicate that the engine is operating in six cylinder mode withcylinder valves deactivated in two cylinders. The amount of time in thefirst cylinder mode begins to increase. The amount of time in the secondcylinder mode remains at zero. The value of VDE_BUSY for the firstcylinder mode continues to decrease and the value of VDE_BUSY for thesecond cylinder mode remains at zero.

At time T1307, the cylinder deactivation request transitions to eight torequest eight active cylinders. The amount of time the engine operatedin the first cylinder mode is long so the value of VDE_BUSY for thefirst mode is revised to a small value. The cylinder activation state istransitioned to a value of eight to indicate that the engine hasactivated all eight cylinders and valves. The amount of time in thesecond cylinder mode is zero and the value of VDE_BUSY for the secondcylinder mode is zero.

At time T1308, the cylinder deactivation request transitions to a valueof six in response to a reduced driver demand torque (not shown). Atnearly the same time, the cylinder activation state also transitions toa value of six based on the cylinder deactivation request. The amount oftime in the first cylinder mode begins to increase and the amount oftime in the second cylinder mode remains at zero. The values of VDE_BUSYfor the first and second valve deactivation modes are zero.

At time T1309, the cylinder deactivation request transitions to a valueof four in response to driver demand torque (not shown). The cylinderactivation state also transitions to a value of four in response to thecylinder deactivation request value. The amount of time in the firstcylinder mode is transitioned to zero and the VDE_BUSY value for thefirst cylinder mode is made zero. The amount of time in the secondcylinder mode begins to increase and the VDE_BUSY value for the secondcylinder valve deactivation mode remains at a value of zero.

At time T1310, the cylinder valve deactivation request transitions backto a value of six in response to the driver demand torque increasing(not shown). The cylinder activation state transitions back to a valueof six in response to the value of the cylinder deactivation request.The value of VDE_BUSY for the second cylinder valve deactivation mode isincreased in response to the short amount of time the engine is operatedin four cylinder mode. The amount of time in the first cylinder modebegins to increase and the amount of time in the second cylinder mode ismade zero.

At time T1311, the cylinder deactivation request transitions back to avalue of four in response to the driver demand torque decreasing (notshown). The cylinder activation state remains at a value of six becausethe value of VDE_BUSY for the second cylinder mode is greater than thevalue of the variable PAYBACK_TIME (not shown). The amount of time inthe first cylinder mode continues to increase and the amount of time inthe second cylinder mode remains at zero. The value of VDE_BUSY for thefirst cylinder valve deactivation mode remains at zero.

At time T1312, the cylinder deactivation request transitions back to avalue of six in response to the driver demand torque increasing (notshown). The cylinder activation state is at a value of six based on thevalue of the cylinder deactivation request. The amount of time in thefirst cylinder mode continues to increase and the amount of time in thesecond cylinder mode is zero. The value of VDE_BUSY for the secondcylinder mode continues to decrease since the engine was nottransitioned out of the second cylinder mode.

At time T1313, the cylinder deactivation request transitions to a valueof four in response to the driver demand torque decreasing (not shown).The cylinder activation state remains at a value of six because thevalue of VDE_BUSY for the second cylinder mode is greater than the valueof the variable PAYBACK_TIME (not shown). Thus, valves of two cylindersare deactivated even though the cylinder deactivation request is at avalue of four. The amount of time in the first cylinder mode continuesto increase and the amount of time in the second cylinder mode remainsat zero. The value of VDE_BUSY for the first cylinder mode remains atzero.

At time T1314, the cylinder deactivation request remains at a value offour and the cylinder activation state transitions to a value of four inresponse to the value of PAYBACK_TIME (not shown). Thus, valves of fourcylinders are deactivated and four cylinders are activated. The amountof time in the first cylinder mode is transitioned to zero and theVDE_BUSY value for the first cylinder mode is made zero. The amount oftime in the second cylinder mode begins to increase and the VDE_BUSYvalue for the second cylinder mode continues to decrease.

At time T1315, the cylinder deactivation request transitions to a valueof eight to request activation of all cylinder valves and cylinders. Thecylinder activation state is transitioned to a value of eight toindicate that all cylinder valves and cylinders are activated. Theamount of time in the second cylinder mode is long so the value ofVDE_BUSY for the second valve mode is made small, thereby permitting aquick transition into four cylinder mode where cylinder valves of fourcylinders are deactivated.

Thus, it may be observed that entry into various cylinder modes may beprevented based on the amount of time in a cylinder mode relative to apayback time. Further, the cylinder modes are not locked out in responseto cylinder mode shifting busyness. Instead, entry into the variouscylinder modes may be delayed for varying amounts of time to reduce adriver's perception of cylinder mode switching busyness.

Referring now to FIG. 14, a method for evaluating engine brake torque inavailable cylinder modes as a basis for selectively allowing cylinderdeactivation is shown. The method of FIG. 14 may be included in thesystem described in FIGS. 1A-6C. The method of FIG. 14 may be includedas executable instructions stored in non-transitory memory. The methodof FIG. 14 may perform in cooperation with system hardware and othermethods described herein to transform an operating state of an engine orits components.

At 1402, method 1400 determines a desired engine torque and presentengine speed. Engine speed may be determined via an engine position orspeed sensor. An amount of time it takes for the engine to travelbetween two positions is the engine speed. The desired engine torque maybe determined from a driver demand torque. In one example, the driverdemand torque is based on accelerator pedal position and vehicle speed.Accelerator pedal position and vehicle speed index a table ofempirically determined driver demand torque values. The driver demandtorque value corresponds to a desired torque at a position along thedriveline. The position along the driveline may be the enginecrankshaft, the transmission input shaft, transmission output shaft, orvehicle wheel. If the driver demand torque is an engine torque, outputfrom the table is the desired or demanded engine torque. Torques atother locations along the driveline may be determined via adjusting adesired torque at one location based on gear ratios, torquemultiplication devices, losses, and torque capacities of clutches.

For example, if driver demand torque is a wheel torque, engine torquemay be determined by multiplying the driver demand torque (or thedesired wheel torque) by the gear ratios between the wheel and theengine. Further, if the driveline includes a torque converter, thedesired wheel torque may be divided by the torque converter torquemultiplication factor to determine engine torque. Torque transferred viaclutches may be estimated as a multiplier. For example, if a clutch isnot slipping torque input to the clutch equals torque output from theclutch and the multiplier value is one. Torque input to the clutchmultiplied by one yields clutch output torque. If the clutch isslipping, the multiplier is a value from 0 to a number less than one.The multiplier value may be based on the clutch's torque capacity.Method 1400 proceeds to 1404.

At 1404, method 1400 determines cylinder modes that may provide thedesired engine torque. In one example, an engine torque table may beprovided that describes maximum engine torque output as a function ofcylinder mode and engine speed. The desired engine torque is compared toengine cylinder valve timing and barometric pressure compensated outputsfrom the engine torque table indexed by the cylinder mode at the presentengine speed, barometric pressure, and cylinder valve timing (e.g.,intake valve closing timing). If the engine torque table outputs atorque value that is greater than the desired engine torque plus anoffset torque, the cylinder mode corresponding to the torque output bythe table may be determined to be a cylinder mode that provides thedesired engine torque. Values stored in the engine torque table may beempirically determined and stored to controller memory.

On example of an engine brake torque table is shown in FIG. 1. It is anengine torque table for a four cylinder engine. The engine torque tablemay include torque output values for three cylinder modes; a mode withtwo active cylinders, a mode with three active cylinders, and a modewith four active cylinders. The engine torque table may also include aplurality of engine speeds. Torque values between the engine speeds maybe interpolated.

Table 1:

TABLE 1 Engine speed 500 1000 2000 3000 4000 Active 2 39 48 52 49 43cylinders 3 58 74 79 76 65 4 77 96 104 100 88Thus, table 1 includes rows of active cylinder modes and columns ofengine speed. Table 1 outputs torque values in units of N-m in thisexample. The engine brake torque values output from the brake torquetable may be adjusted by functions based on spark timing from minimumspark for best torque (MBT), intake valve closing time from a nominalintake valve closing time, engine air-fuel ratio, and enginetemperature. The functions output empirically determined multipliersthat modify the engine brake torque value output from the engine braketorque table. The desired engine brake torque is compared to themodified value output from the engine brake torque table. Note that adesired wheel torque may be converted to a desired engine torque viamultiplying the desired wheel torque by the gear ratio between thewheels and the engine. Further, determining engine torque may includemodifying the wheel torque according to the torque multiplication of thetransmission torque converter. Additionally, or alternatively, cylindermodes that include different firing orders or active cylinders in anengine cycle may also be a basis for indexing and storing values in anengine brake torque table. Method 1400 proceeds to 1406.

At 1406, method 1400 allows cylinder modes that provide the desiredengine torque to be allowed. Allowed cylinder modes may be activated at716 of FIG. 7.

An example using table 1: table 1 is indexed by engine speed andcylinder mode. The cylinder mode begins at a minimum value, two in thisexample, and it incremented until it reaches the maximum cylinder mode.For example, if the engine is operating at 1000 RPM and the desiredengine torque is 54 N-m, table 1 outputs a value of 48 N-m correspondingto 1000 RPM and cylinder mode two (e.g., two active cylinders), 74 N-mcorresponding to 1000 RPM and cylinder mode three (e.g., three activecylinders), and 96 N-m corresponding to 1000 RPM and cylinder mode four(e.g., four active cylinders). The cylinder mode with two activecylinders at 1000 RPM is not allowed because two active cylinders lackcapacity to provide the desired 74 N-m of torque. Cylinder modes withthree and four cylinders are allowed. In some examples, the desiredengine torque plus a predetermined offset is compared to values outputfrom the table. If the desired engine torque plus the predeterminedoffset is greater than an output from the table, the cylinder modecorresponding to the table output is not allowed. Allowed and notallowed cylinder modes may be indicated by values of variables stored inmemory. For example, if three cylinder mode is allowed at 1000 RPM, avariable in memory corresponding to three cylinder mode at 1000 RPM maybe populated with a value of one. If cylinder mode three is not allowedat 500 RPM, a variable in memory corresponding to cylinder mode three at500 RPM may be populated with a value of zero. Method 1400 proceeds toexit.

Thus, engine cylinder modes and engine brake torque available in thecylinder modes may be a basis for determining which cylinder mode theengine operates with. Further, cylinder modes with lower fuelconsumption may be given selection priority so that fuel may beconserved.

Referring now to FIG. 15, a method for evaluating engine fuelconsumption in available cylinder modes as a basis for selectivelyallowing cylinder deactivation is show. The method of FIG. 15 may beincluded in the system described in FIGS. 1A-6C. The method of FIG. 15may be included as executable instructions stored in non-transitorymemory. The method of FIG. 15 may perform in cooperation with systemhardware and other methods described herein to transform an operatingstate of an engine or its components.

At 1502, method 1500 determines a desired engine torque and presentengine speed. Engine speed may be determined via an engine position orspeed sensor. Method 1500 proceeds to 1504.

At 1504, method 1500 determines cylinder modes that may provide thedesired engine torque. In one example, cylinder modes that may providethe desired engine torque are determined as described in FIG. 14.

At 1506, method 1500 estimates fuel consumption in cylinder modes thatare allowed. The allowed cylinder modes are from 1406 of FIG. 14. In oneexample, a brake specific fuel table or function indexed by cylindermodes from the allowed cylinder modes from FIG. 14, engine speed, anddesired engine torque outputs a brake specific fuel consumption value.Values stored in the brake specific fuel table may be empiricallydetermined and stored to controller memory. The brake specific fuelconsumption value may be adjusted by functions based on spark timingfrom minimum spark for best torque (MBT), intake valve closing time froma nominal intake valve closing time, engine air-fuel ratio, and enginetemperature. The functions output empirically determined multipliersthat modify the brake specific fuel consumption value output from thetable. Brake specific fuel values for each allowed cylinder mode at thepresent engine speed are output from the brake specific fuel table. Forexample, from the example described at 1406, the actual number of activecylinders is three and four since three and four cylinder modes providethe desired engine torque. Method 1500 proceeds to 1508.

At 1508, method 1500 compares fuel consumption for the allowed cylindermodes that can provide the requested torque. In one example, the presentengine fuel consumption, which may be determined by the present enginefuel flow rate, is compared to values output from the brake specificfuel table for allowed cylinder modes. The comparison may be performedby subtracting values output from the brake specific fuel table from thepresent engine fuel consumption rate. Alternatively, the comparison maybe based on dividing the present engine fuel consumption value by thevalues output from the brake specific fuel table. Cylinder modes thatprovide greater than a threshold percentage improvement in engine fueleconomy over the present cylinder mode are allowed.

Thus, cylinder modes and fuel consumption in the cylinder modes may be abasis for determining which cylinder mode the engine operates with.Further, cylinder modes with lower fuel consumption may be givenselection priority so that fuel may be conserved.

Referring now to FIG. 16, a method for evaluating a rate of cam phasingfor cam torque actuated cam phase adjustments is shown. The method ofFIG. 16 may be included in the system described in FIGS. 1A-6C. Themethod of FIG. 16 may be included as executable instructions stored innon-transitory memory. The method of FIG. 16 may perform in cooperationwith system hardware and other methods described herein to transform anoperating state of an engine or its components. Method 1600 may beperformed for each engine camshaft.

At 1602, method 1600 determines engine conditions. Engine conditions mayinclude but are not limited to an actual total number of cylinder valvesthat are deactivated during an engine cycle, engine speed, driver demandtorque, vehicle speed, engine temperature, and ambient temperature.Method 1600 proceeds to 1604 after operating conditions are determined.

At 1604, method 1600 judges if one or more cylinder valves isdeactivated. Method 1600 may judge that one or more cylinder isdeactivated based on a value of a bit stored in memory, output of asensor that measures valve operator position, cylinder pressure sensors,or other sensors. If method 1600 judges that one or more cylinder valvesis deactivated, the answer is yes and method 1600 proceeds to 1606.Otherwise, the answer is no and method 1600 proceeds to 1634.

At 1606, method 1600 judges if a camshaft position adjustment relativeto crankshaft position is desired. For example, method 1600 judges if itis desirable to advance camshaft timing 5 degrees relative to crankshafttiming so that intake or exhaust valves open 5 crankshaft degrees soonerafter camshaft position is adjusted. The camshaft position may beadjusted in response to driver demand torque and engine speed. If driverdemand torque is increasing rapidly and engine speed is increasingrapidly, it may be desirable to adjust camshaft position relative tocrankshaft position at a higher rate of speed so that the engineprovides a desired amount of torque and engine emissions. In oneexample, method 1600 determines if a camshaft position adjustment isdesired based on a current camshaft position relative to crankshaftposition and a change in driver demand torque and engine speed. Ifmethod 1600 judges that a camshaft position adjustment is desired, theanswer is yes and method 1600 proceeds to 1608. Otherwise, the answer isno and method 1600 proceeds to 1634. In some examples, 1606 may beomitted and method 1600 may simply proceed to 1608.

At 1608, method 1600 determines a desired rate of camshaft positionchange relative to crankshaft position. In one example, method 1600determines a desired rate of camshaft position change based on a rate ofchange in driver demand torque. If the rate of change of driver demandtorque is low, the rate of change of camshaft position relative tocrankshaft position is low. If the rate of change of driver demandtorque is high, the rate of camshaft position change relative tocrankshaft position is high. For example, the camshaft may be advancedat 0.5 crankshaft degrees per second when a change in driver demandtorque is low (e.g., 5 N-m/second). However, if the change in driverdemand torque is high (e.g., 200 N-m/second), the camshaft may beadvanced at 5 crankshaft degrees per second In one example, the desiredrate of camshaft position change relative to crankshaft position isempirically determined and stored to memory in a table or function. Thetable or function is indexed based on a rate of change in driver demandtorque, the table or function outputs a desired rate of camshaftposition change relative to crankshaft position. Method 1600 proceeds to1610 after the desired rate of camshaft position change is determined.

At 1610, method 1600 judges if an actual total number of active cylindervalves (e.g., valves that open and close during an engine cycle)presently operating is sufficient to move the camshaft relative to thecrankshaft at the desired rate. In one example, a table or functiondescribes camshaft rate of position change relative to the crankshaftposition based on an actual total number of active cylinder valves. Thetable is indexed via the actual total number of active valves and itoutputs a rate of camshaft position change relative to crankshaftposition. Values in the table or function are empirically determined andstored in memory. Output from the table or function is compared to thevalue determined at 1608. If the camshaft rate of position change from1610 is greater than the camshaft rate of position change from 1608, theanswer is yes and method 1600 proceeds to 1634. Otherwise, the answer isno and method 1600 proceeds to 1612.

At 1612, method 1600 judges if the camshaft operates both intake andexhaust valves. In one example, a bit in memory identifies the camshaftas operating only intake valves if a value of the bit is zero. If thevalue of the bit is one, the camshaft operates both intake and exhaustvalves. If method 1600 judges that the camshaft operates intake andexhaust valves, the answer is yes and method 1600 proceeds to 1630.Otherwise, the answer is no and method 1600 proceeds to 1614.

At 1614, method 1600 judges if the camshaft is an intake camshaft.Method 1600 may judge if the camshaft is an intake camshaft based on avalue of a bit stored in memory. The bit may be programed at time ofmanufacture. If method 1600 judges that the camshaft is an intakecamshaft, the answer is yes and method 1600 proceeds to 1616. Otherwise,the answer is no and method 1600 proceeds to 1620.

At 1620, method 1600 authorizes activating one or more deactivatedexhaust valves. In one example, the desired rate of exhaust camshaftposition change relative to crankshaft position determined at 1608 isused to index a table or function of empirically determined values thatdescribe an actual total number of valves that have to operate toprovide the desired rate of exhaust camshaft position adjustmentrelative to crankshaft position. Method 1600 requests or authorizesoperation of the actual total number of exhaust valves output from thetable or function. The exhaust valves may be activated with or withoutactivating cylinders that include the exhaust valves being activated. Ifthe driver demand torque is increasing, the cylinders with exhaustvalves being activated may be activated to increase engine torque whileincreasing the camshaft position change. If the driver demand torque isdecreasing, the cylinders with exhaust valves being activated may not beactivated so that fuel consumption may be reduced. Method 1600 proceedsto 1634.

At 1634, method 1600 moves the camshaft and operates valves foroperating conditions after the camshaft is moved. The camshaft may bemoved while valves are being activated to move the camshaft to a desiredposition as soon as possible. After the camshaft reaches its desiredposition relative to the crankshaft position, cylinder valves may bedeactivated based on vehicle conditions other than the desired rate ofcamshaft position change. In this way, valves may be reactivated toimprove a rate that a camshaft position moves relative to a crankshaftposition. The engine cylinders may also be reactivated when the cylindervalves are reactivated. Method 1600 proceeds to exit after the camshaftbegins to move to its desired new position based on driver demand torqueand engine speed.

At 1616, method 1600 authorizes activating one or more deactivatedintake valves. In one example, the desired rate of intake camshaftposition change relative to crankshaft position determined at 1608 isused to index a table or function of empirically determined values thatdescribe an actual total number of valves that have to operate toprovide the desired rate of intake camshaft position adjustment relativeto crankshaft position. Method 1600 requests or authorizes operation ofthe actual total number of intake valves output from the table orfunction. The cylinders that include the intake valves that are beingactivated may be activated or they may not combust air and fuel duringengine cycles when the intake valves are being operated. In one example,the cylinders with intake valves being activated combusts air and fuelduring engine cycles in response to an increase in driver demand torque.The cylinders with intake valves being activated may not combust air andfuel during engine cycles in response to a decrease in driver demandtorque. Deactivated intake valves may be activated as described at FIG.22.

In addition, method 1600 may increase an amount of boost provided to theengine so that the additional boost may blow exhaust gases from thecylinder before the exhaust valve of the cylinder being reactivated isclosed. By clearing exhaust gases from the cylinder, combustionstability may improve and the cylinder may provide additional power.Additionally, an amount of overlap (e.g., open time) between thecylinder's intake valves and exhaust valves may be increased to furtherallow pressurized air from the intake manifold to clear out the cylinderbeing activated. Method 1600 proceeds to 1634 after intake valves areactivated.

At 1630, method 1600 judges if engine noise vibration and harshness(NVH) are less than threshold levels if one or more cylinders arereactivated and combustion occurs in the reactivated cylinders. In oneexample, method 1600 judges if reactivating one or more cylindersincluding combusting air and fuel in the reactivated cylinders willproduce NVH greater than is desired based on output of a table orfunction that describes engine and/or powertrain NVH. The table isindexed via engine speed, driver demand torque, and cylinder mode beingactivated (e.g., four or six cylinder mode). The table outputs anumerical value that is empirically determined, via a microphone oraccelerometer for example. If the output value is less than a thresholdvalue, the answer is yes and method 1600 proceeds to 1632. Otherwise,the answer is no and method 1600 proceeds to 1640.

At 1632, method 1600 authorizes activating one or more cylinder viaactivating the cylinder's valves and supplying fuel, air, and spark tothe cylinder. The cylinder begins combusting air and fuel when it isreactivated. Thus, if reactivating one or more cylinders to increasecamshaft rate of position change produces little objectionable NVH, thecylinder is reactivated via reactivating the cylinder's valves andbeginning combustion in the reactivated cylinder. Method 1600 proceedsto 1634.

At 1640, method 1600 authorizes activating one or more valves of adeactivated cylinder that is not combusting air and fuel. If thecylinder includes deactivated intake and exhaust valves, only thecylinders exhaust valves may be activated to improve the rate ofcamshaft position adjustment relative to crankshaft position. Byreactivating only exhaust valves of the cylinder, cam torque may beincreased to improve the camshaft position adjustment relative tocrankshaft position without flowing air through the cylinder. Stoppingair flow through the cylinder may help to keep catalyst temperatureelevated and maintain a desired amount of oxygen in the catalyst. Ifboth intake and exhaust valves of the cylinder are reactivated, air mayflow through the cylinder after the intake and exhaust valves areactivated. Spark and fuel are not supplied to the cylinders withreactivated valves so that NVH may not degrade. Method 1600 proceeds to1642.

At 1642, method 1600 increases an amount of fuel delivered to an activecylinder combusting air and fuel to richen the mixture combusted by theactive cylinder if air is flowing through the cylinder with one or morevalves authorized to be activated at 1640. By richening the mixture ofan active cylinder combusting air and fuel while air flows through acylinder, it may be possible to maintain desired levels of hydrocarbonsand oxygen in a catalyst so that the catalyst may convert exhaust gasesefficiently. For example, if cylinder number eight of an eight cylinderengine has its intake and exhaust valves reactivated while cylindernumber eight is not combusting air and fuel, the air-fuel ratio ofcylinder number one that is combusting air and fuel may be richened toimprove or maintain catalyst efficiency. Method 1600 proceeds to 1634after enriching at least one cylinder's air-fuel ratio.

Referring now to FIG. 17, a sequence for operating an engine accordingto the method of FIG. 16 is shown. The vertical lines at timeT1700-T1704 represent times of interest in the sequence. FIG. 17 showssix plots and the plots are time aligned and occur at the same time. Inthis example, the engine is a four cylinder engine with a firing orderof 1-3-4-2. Cylinders 2 and 3 have deactivating valve operators fordeactivating cylinders 3 and 4. Valves of cylinders 1 and 4 alwaysremain active.

The first plot from the top of FIG. 17 is a plot of a camshaft movementrequest versus time. A camshaft movement request is a request to changea position of a camshaft relative to a position of a crankshaft Forexample, if a camshaft has a lobe that begins to open an intake valve ofcylinder number one of an engine 370 crankshaft degrees beforetop-dead-center compression stroke (e.g., position of crankshaft zerodegrees), the position of the camshaft may be moved relative to thecrankshaft so that the camshaft lobe begins to open the intake valve ofcylinder number one of the engine at 380 crankshaft degrees beforetop-dead-center compression stroke. Thus, in this example, the relativeposition of the camshaft is advanced 10 crankshaft degrees relative tothe crankshaft position.

The vertical axis represents the camshaft move request. The cam moverequest trace is at a higher level and asserted when it is desired tomove the engine camshaft relative to the engine crankshaft. The cam moverequest trace is at a lower level and not asserted when it is notdesired to move the engine camshaft relative to the engine crankshaft.The horizontal axis represents time and time increases from the leftside of the figure to the right side of the figure.

The second plot from the top of FIG. 17 is a plot of camshaft positionversus time. The vertical axis represents camshaft position and thecamshaft is more advanced in the direction of the vertical axis arrow.The horizontal axis represents time and time increases from the leftside of the figure to the right side of the figure.

The third plot from the top of FIG. 17 is a plot of deactivatingcylinder intake valve state. In this example, the deactivating cylindermay be cylinder number two or cylinder number three. The deactivatingcylinder intake valve state indicates whether or not the intake valve ofthe deactivating cylinder is activated (e.g., opening and closing duringan engine cycle) or deactivated (e.g., held closed during an entireengine cycle). The vertical axis represents deactivating cylinder intakevalve state. The deactivating cylinder intake valve is active when thetrace is at a higher level near the vertical axis arrow. Thedeactivating cylinder intake valve is deactivated when the trace is at alower level near the horizontal axis. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

The fourth plot from the top of FIG. 17 is a plot of deactivatingcylinder exhaust valve state. In this example, the deactivating cylindermay be cylinder number two or cylinder number three. The deactivatingcylinder exhaust valve state indicates whether or not the exhaust valveof the deactivating cylinder is activated (e.g., opening and closingduring an engine cycle) or deactivated (e.g., held closed during anengine cycle). The vertical axis represents deactivating cylinderexhaust valve state. The deactivating cylinder exhaust valve is activewhen the trace is at a higher level near the vertical axis arrow. Thedeactivating cylinder exhaust valve is deactivated when the trace is ata lower level near the horizontal axis. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

The fifth plot from the top of FIG. 17 is a plot of deactivatingcylinder fuel flow state. In this example, the deactivating cylinder maybe cylinder number two or cylinder number three. The deactivatingcylinder fuel flow state indicates whether or not the fuel is flowing tothe deactivating cylinder. The vertical axis represents deactivatingcylinder fuel flow state. Fuel is flowing to the deactivating cylinderwhen the deactivating cylinder fuel flow trace is at a higher level nearthe vertical axis arrow. Fuel is not flowing to the deactivatingcylinder when the deactivating cylinder fuel flow trace is at a lowerlevel near the horizontal axis. The horizontal axis represents time andtime increases from the left side of the figure to the right side of thefigure.

The sixth plot from the top of FIG. 17 is a plot of active cylinder fuelair-fuel ratio. In this example, the active cylinder may be cylindernumber 1 or cylinder number 4. The vertical axis represents activecylinder air-fuel ratio and the air-fuel ration increases (e.g., becomeleaner) in the direction of the vertical axis arrow. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure. Horizontal line 1702 represents astoichiometric air-fuel ratio.

At time T1700, there is not a camshaft move request and the camshaft isrelatively retarded. The deactivating cylinder intake valve stateindicates that the deactivating cylinder intake valve is deactivated(e.g., not opening during a cycle of the engine). The deactivatingcylinder exhaust valve state indicates that the deactivating cylinderexhaust valve is deactivated (e.g., not opening during a cycle of theengine). The active cylinder is operating at a stoichiometric air-fuelratio and no fuel flows to the deactivating cylinder as indicated by thedeactivating cylinder fuel flow state being at a low level.

At time T1701, the camshaft move request is asserted requesting acamshaft position change relative to a position of the enginecrankshaft. The request may be initiated via an increase in a driverdemand torque or a change in another operating condition. The rate ofchange in position of the engine camshaft relative to the position ofthe engine crankshaft (not shown) is greater than that which may beaccomplished with the deactivating cylinder intake and exhaust valvesdeactivated since operating fewer valves provides less torque to actuatecamshaft motion. Therefore, the deactivating cylinder's intake andexhaust valves are reactivated as indicated by the deactivating cylinderintake valve state and exhaust valve state transitioning to higherlevels to indicate the intake and exhaust valves of the deactivatingcylinder are reactivated. Additionally, fuel flows to the deactivatingcylinder and combustion begins in the deactivating cylinder (not shown).The camshaft position is advanced while the deactivating cylinder intakeand exhaust valves are activated. The air-fuel ratio of the activecylinders is stoichiometric.

At time T1702, the camshaft move request transitions to a not assertedstate. The camshaft move request may transition to not asserted when thecamshaft reaches its destination. Further, fuel stops flowing to thedeactivating cylinder and combustion stops in the deactivating cylinder(not shown). The camshaft position reaches a middle advanced positionand is maintained at its position. The air-fuel ratios of the activecylinders remain stoichiometric.

At time T1703, the camshaft move request is asserted again requesting acamshaft position change relative to a position of the enginecrankshaft. The request may be initiated via an increase in a driverdemand torque or a change in another operating condition. The rate ofchange in position of the engine camshaft relative to the position ofthe engine crankshaft (not shown) is greater than that which may beaccomplished with the deactivating cylinder intake and exhaust valvesdeactivated since operating fewer valves provides less torque to actuatecamshaft motion. As a result, the deactivating cylinder's intake andexhaust valves are reactivated as indicated by the deactivating cylinderintake valve state and exhaust valve state transitioning to higherlevels to indicate the intake and exhaust valves of the deactivatingcylinder are reactivated. Fuel flow to the deactivating cylindersremains stopped. In this example, combustion is not reinitiated in thedeactivating cylinders because reactivating the deactivating cylindersis expected to produce NVH levels greater than is desired. The camshaftposition is advanced while the deactivating cylinder intake and exhaustvalves are activated. The air-fuel ratio of the active cylinders isenrichened so that when the richened exhaust from the activatedcylinders meets with oxygen from the deactivating cylinders, astoichiometric exhaust gases are provided to the catalyst.

At time T1704, the camshaft move request transitions to a not assertedstate. The camshaft move request may transition to not asserted when thecamshaft reaches its destination Further, the deactivating cylinder'sintake and exhaust valves are deactivated as indicated by thedeactivating cylinder intake and exhaust valve states. The camshaftposition reaches a fully advanced position and is maintained at itsposition. The air-fuel ratios of the active cylinders transition back toa stoichiometric air-fuel ratio by leaning the air-fuel mixtures of thedeactivating cylinders.

In this way, cylinder intake and exhaust valves that have beendeactivated may be reactivated to provide more rapid positionadjustments to the engine camshaft. Further, stoichiometric exhaustgases may be provided to a catalyst to maintain catalyst efficiencywhether air or exhaust gases flow from deactivating cylinders.

Referring now to FIG. 18, a method for judging whether or not to shifttransmission gears when evaluating cylinder mode changes is shown. Themethod of FIG. 18 may be included in the system described in FIGS.1A-6C. The method of FIG. 18 may be included as executable instructionsstored in non-transitory memory. The method of FIG. 18 may perform incooperation with system hardware and other methods described herein totransform an operating state of an engine or its components.

At 1802, method 1800 determines a desired wheel torque. In one example,desired wheel torque is determined based on accelerator pedal positionand vehicle speed. For example, accelerator pedal position and vehiclespeed index a table that outputs desired wheel torque. Values in thetable may be empirically determined and stored to controller memory. Inother examples, accelerator pedal position and vehicle speed may index atable that outputs desired engine brake torque or torque at anotherlocation of the driveline (e.g., transmission input shaft). The outputfrom the table is multiplied by gear ratios between the torque location(e.g., engine), torque converter multiplication, and driveline torquelosses to estimate desired wheel torque. Method 1800 proceeds to 1804.

At 1804, method 1800 determines the presently selected transmissiongear. Method 1800 may determine the presently selected transmission gearvia a value of a location in controller memory. For example, a variablein memory may range from a value of 1-10, which indicates the presentlyselected gear ratio. Method 1800 proceeds to 1806.

At 1806, method 1800 estimates engine fuel consumption in cylinder modesthat may provide the desired wheel torque the present transmission gear.Method 1800 determined engine brake specific fuel consumption in thepresent transmission gear according to the method of FIG. 15. Method1800 proceeds to 1808.

At 1808, method 1800 estimates engine fuel consumption in cylinder modesthat may provide the desired wheel torque the next higher transmissiongear. For example, if the transmission is presently in 3^(rd) gear,engine fuel consumption to provide equivalent wheel torque with thetransmission in 4^(th) gear is determined. In one example, method 1800determines engine brake specific fuel consumption in the next highertransmission gear as follows: the present vehicle speed is divided bythe gear ratio between engine and the wheels including the next highertransmission gear to estimate the engine speed in the next highertransmission gear. The present wheel torque is divided by the gear ratiobetween the engine and the wheels to estimate engine torque forproviding equivalent wheel torque in the next higher transmission gear.The gear ratio between the engine and the wheels may also be compensatedfor the torque converter if one is present. Method 1800 determinescylinder modes that may provide the desired wheel torque in the nexthigher transmission gear according to the method of FIG. 14 using theestimate of engine torque in the next higher gear that providesequivalent wheel torque to the present wheel torque. Note that thepresent wheel torque may be the desired wheel torque. The estimatedengine fuel consumption is then determined as described in thedescription of the method of FIG. 15. Method 1800 proceeds to 1810.

At 1810, method 1800 estimates engine fuel consumption in cylinder modesthat may provide the desired wheel torque the next lower transmissiongear. For example, if the transmission is presently in 3^(rd) gear,engine fuel consumption to provide equivalent wheel torque with thetransmission in 2nd gear is determined. In one example, method 1800determines engine brake specific fuel consumption in the next lowertransmission gear as follows: the present vehicle speed is divided bythe gear ratio between engine and the wheels including the next lowertransmission gear to estimate the engine speed in the next highertransmission gear. The present wheel torque is divided by the gear ratiobetween the engine and the wheels to estimate engine torque forproviding equivalent wheel torque in the next lower transmission gear.The gear ratio between the engine and the wheels may also be compensatedfor the torque converter if one is present. Method 1800 determinescylinder modes that may provide the desired wheel torque in the nextlower transmission gear according to the method of FIG. 14 using theestimate of engine torque in the next lower gear that providesequivalent wheel torque to the present wheel torque. Note that thepresent wheel torque may be the desired wheel torque. The estimatedengine fuel consumption is then determined as described in thedescription of the method of FIG. 15. Method 1800 proceeds to 1812.

In some examples, method 1800 estimates engine fuel consumption incylinder modes that may provide the desired wheel torque for alltransmission gears. For example, if the transmission is presently in3^(rd) gear, and the transmission includes five forward gears, enginefuel consumption to provide equivalent wheel torque with thetransmission in gears 1, 2, 4, and 5 is determined. In this way, it maybe possible to select whichever gear provides the most improvement invehicle fuel economy.

At 1812, method 1800 allows activation of transmission gears andcylinder modes that provide greater than a threshold percentage ofdecrease in engine fuel consumption as compared to present cylinder modeand transmission gear. In one example, brake specific engine fuelconsumption in engine cylinder modes that provide the desired enginetorque or wheel torque in the next higher transmission gear are dividedby the brake specific engine fuel consumption in the present cylindermode and present transmission gear. If the result is greater than athreshold, the engine cylinder modes that provide the desired enginetorque or wheel torque in the next higher transmission gear are allowed.Likewise, engine fuel consumption in engine cylinder modes that providethe desired engine torque or wheel torque in the next lower transmissiongear are compared to engine fuel consumption in the present cylindermode and present transmission gear. If the result is greater than athreshold, the engine cylinder modes that provide the desired enginetorque or wheel torque in the next lower transmission gear are allowed.Additionally, method 1800 may require that an expected noise level andan expected vibration level in a new gear (e.g., a higher or lower gearthan the present transmission gear) are less than threshold values ofnoise and vibration. Noise and vibration levels may be assessed asdescribed at FIG. 22. Further, if an engine knock sensor or other sensordetects engine vibration greater than a threshold after changingtransmission gears, the transmission may be shifted back to its formergear state.

Referring now to FIG. 19, a sequence for operating an engine accordingto the method of FIG. 18 is shown. The vertical lines at timeT1900-T1905 represent times of interest in the sequence. FIG. 19 showsfour plots and the plots are time aligned and occur at the same time. Inthis example, the vehicle is being maintained at a constant speed andrequested wheel torque is varied to maintain the constant vehicle speed.The vehicle has a four cylinder engine.

The first plot from the top of FIG. 19 is a plot of a requested wheeltorque versus time. In one example, requested wheel torque is based onaccelerator pedal position and vehicle speed. Requested wheel torqueincreases in the direction of the vertical axis arrow. The horizontalaxis represents time and time increases from the left side of the figureto the right side of the figure.

The second plot from the top of FIG. 19 is a plot of active transmissiongear versus time. The vertical axis represents presently activetransmission gear and transmission gears are indicated along thevertical axis. The horizontal axis represents time and time increasesfrom the left side of the figure to the right side of the figure.

The third plot from the top of FIG. 19 is a plot of the actual totalnumber of active engine cylinders versus time. The actual total numberof active engine cylinders is listed along the vertical axis. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure.

The fourth plot from the top of FIG. 19 is a plot of estimated enginefuel consumption versus time. The vertical axis represents estimatedengine fuel consumption and estimated engine fuel consumption increasesin the direction of the vertical axis arrow. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure. Trace 1902 represents engine fuelconsumption if the engine is operated with the transmission in thirdgear. Trace 1904 represents engine fuel consumption of the engine isoperated with the transmission in second gear.

At time T1900, the requested wheel torque is a lower middle level andthe transmission is in third gear. The actual total number of activeengine cylinders is two and the estimated engine fuel consumption is amiddle level.

Between time T1900 and time T1901, the requested wheel torque graduallyincreases. The active or present transmission gear is third gear and theactual total number of active engine cylinders is two. The estimatedengine fuel consumption for operating the engine in second gear isgreater than the estimated engine fuel consumption for operating theengine in third gear.

At time T1901, the wheel torque has increased to a value where theestimated engine fuel consumption for operating the engine while thetransmission is in second gear is less than the estimated fuelconsumption for operating the engine while the transmission is in thirdgear. Therefore, the transmission is downshifted to increase vehiclefuel efficiency. The number of active cylinders remains at a value oftwo and the estimated fuel consumption increases as the requested wheeltorque increases.

At T1902, the number of active cylinders increases from two to three inresponse to the increase in requested wheel torque. The requested wheeltorque and engine fuel consumption continue to increase. Thetransmission remains in second gear.

At T1903, the number of active cylinders increases from three to four inresponse to the increase in requested wheel torque. The requested wheeltorque and engine fuel consumption continue to increase. Thetransmission remains in second gear as the requested wheel torqueincreases.

At time T1904, the requested wheel torque is decreasing and it hasdecreased to a level where the estimated engine fuel consumption foroperating the vehicle in third gear is less than the estimated enginefuel consumption for operating the vehicle in second gear. Therefore,the transmission gear is changed to third gear. The actual total numberof active cylinders is also decreased in response to the decreasingrequested wheel torque.

At 1904, the requested wheel torque has decreased to a level where theactual total number of active cylinders is reduced from three to two.The transmission remains in third gear and the estimated engine fuelconsumption decreases with the decrease in requested engine torque.

Referring now to FIG. 20, a method for evaluating tow/haul modes forselecting cylinder mode or VDE mode is shown. The method of FIG. 20 maybe included in the system described in FIGS. 1A-6C. The method of FIG.20 may be included as executable instructions stored in non-transitorymemory. The method of FIG. 20 may perform in cooperation with systemhardware and other methods described herein to transform an operatingstate of an engine or its components.

It may be more desirable to operate a cylinder with intake and exhaustvalves closed and with air or exhaust trapped in the cylinder during anengine cycle because the vehicle may coast for a longer amount of timesince the trapped air or exhaust provides a spring like functionreducing the cylinder's braking torque. Further, closing the intake andexhaust valves limits air flow to the catalyst in the exhaust system sothat excess fuel may not have to be added to engine exhaust to consumeexcess oxygen in the catalyst. However, during tow/haul and hill descentmodes, it may be desirable to provide higher levels of cylinder brakingtorque so it may be desirable to open and close intake and exhaustvalves.

At 2002, method 2000 judges if the engine is or should be indeceleration fuel cut off mode. In deceleration fuel cut off mode, oneor more engine cylinders may be deactivated by stopping fuel flow to thecylinders. Further, gas flow through one or more cylinders may bestopped via deactivating intake valves or intake and exhaust valves of acylinder being deactivated in closed positions as the engine rotatesthrough an engine cycle. Thus, deactivated cylinders are not combustingair and fuel. In one example, method 2000 judges that the engine shouldbe in a deceleration fuel cut off mode when driver demand decreases froma higher value to a lower value and vehicle speed is greater than athreshold speed. If method 2000 judges that the engine should be indeceleration fuel cut off mode, the answer is yes and method 2000proceeds to 2004. Otherwise, the answer is no and method 2000 proceedsto 2020.

At 2020, method 2000 operates all engine cylinders and all cylindervalves are activated. Further, all engine cylinders combust air and fuelmixtures. Alternatively, less than all engine cylinders may be activatedif the driver torque demand is low. Method 2000 proceeds to exit aftercylinders are activated.

At 2004, method 2000 judges if the vehicle is in a tow or haul mode. Inone example, method 2000 judges that the vehicle is in a tow or haulmode based on an operating state of a pushbutton, switch, or variable inmemory. If method 2000 judges that the vehicle is in a tow or haul mode,the answer is yes and method 2000 proceeds to 2006. Otherwise, theanswer is no and method 2000 proceeds to 2030.

A vehicle may have a transmission that shifts according to a first shiftschedule (e.g., transmission shifts are based on driver demand torqueand vehicle speed) when the vehicle is not in a tow or haul mode. Thevehicle's transmission shifts according to a second shift schedule in atow or haul mode. The second shift schedule may upshift at higher driverdemand torques and higher vehicle speeds than the first shift schedule.The second shift schedule may downshift at higher vehicle speeds toincrease driveline braking.

At 2006, method 2000 determines a desired engine brake torque amount forcylinders not combusting air and fuel. In one example, the desiredengine brake torque amount may be empirically determined input to atable or function. The table or function may be indexed via driverdemand torque, vehicle speed, and transmission gear. The table outputsthe desired engine brake torque (e.g., negative torque the engineprovides to the driveline to decelerate the vehicle driveline). Method2000 proceeds to 2008 after determining the desired engine brake torque.

At 2008, method 2000 shifts transmission gears according to a secondgear shift schedule. For example, the transmission may upshift fromfirst to second gear at a driver demand torque of greater than 50 N-mand a vehicle speed of 16 KPH. The second transmission gear shiftschedule up-shifts transmission gears at higher engine speeds and highervehicle speeds than the first transmission gear shift schedule. Thesecond transmission gear shift schedule also downshifts transmissiongears at higher engine speeds and higher vehicle speeds than the firsttransmission shift schedule to provide additional engine braking thanthe first transmission gear shift schedule. The second transmission gearshift schedule up-shifts transmission gears at lower engine speeds andlower vehicle speeds than the third transmission gear shift schedule.The second transmission gear shift schedule downshifts transmissiongears at lower engine speeds and lower vehicle speeds than the thirdtransmission shift schedule to provide less engine braking than thethird transmission gear shift schedule. Method 2000 proceeds to 2010after shifting transmission gears according to the second transmissionshift schedule.

At 2010, method 2000 determines the cylinder deactivation mode of eachdeactivated cylinder to achieve the desired engine brake torque providedvia deactivated cylinders. Note that the cylinder deactivation mode isdifferent than the cylinder mode. The cylinder deactivation mode defineshow valves of a deactivated cylinder are operated whereas the cylindermode defines the actual total number of active cylinders and thecylinders that are active. In one example, a cylinder with intake andexhaust valves that open and close during an engine cycle without fuelinjection (e.g., a first cylinder deactivation mode) and combustion isassigned a first brake torque. A cylinder with intake valves that areheld closed over an engine cycle and exhaust valves that open and closeover the engine cycle without fuel injection (e.g., a second cylinderdeactivation mode) is assigned a second brake torque. A cylinder withintake and exhaust valves that are held closed over an engine cyclewithout fuel injection (e.g., a third cylinder deactivation mode) isassigned a third brake torque. The first brake torque is greater thanthe second brake torque, and the second brake torque is greater than thethird brake torque. Thus, the engine cylinders may provide three levelsof brake torque in three different cylinder deactivation modes, and thedesired brake torque may be provided by operating different cylinders atdifferent brake torque producing levels.

Further, the assigned brake torque values for each of the three cylinderdeactivation modes may be adjusted via adjusting intake valve closingtiming. For example, the assigned brake torque values may be increasedvia retarding intake valve closing timing. Similarly, the assigned braketorque values may be decreased via advancing intake valve closingtiming. In one example, a valve timing compensation function indexed viaintake valve closing timing outputs a value that is multiplied by theassigned first brake torque, the assigned second brake torque, and theassigned third brake torque to provide valve timing compensated cylinderbrake torque values used to determine valve timing compensated braketorque values provided by the cylinders in the different cylinder modes.Additionally, a barometric pressure compensation function indexed bybarometric pressure outputs a value that is multiplied by the valvetiming compensated brake torque values to provide barometric pressureand valve timing compensated brake torque values provided by thecylinders in the different cylinder deactivation modes Intake andexhaust valve timings for each cylinder deactivation mode may beadjusted to increase or decrease braking torque provided by the threecylinder deactivation modes based on barometric pressure and the desiredengine brake torque. For example, if the barometric pressure decreasesand desired brake torque increases, intake valve timing in each of thethree cylinder deactivation modes may be retarded to compensate forlower barometric pressure and higher desired braking torque.

In one example, method 2000 determines valve operation for the enginecylinders according to the desired engine brake torque and the amount ofvalve timing and barometric pressure compensated brake torque eachcylinder provides in the different operating modes. For example, for afour cylinder engine where the desired engine brake torque is 2.5 N-m,the deactivation modes of each cylinder are based on the valve timingand barometric pressure compensated brake torques the cylinders providein the three different cylinder deactivation modes described above. If acylinder provides 0.25 N-m of brake torque in the first cylinderdeactivation mode, 0.5 N-m in second cylinder deactivation mode, and 1N-m in the third cylinder deactivation mode, the four cylinder engine isoperated with two cylinders in the third cylinder deactivation mode andtwo cylinders in the first cylinder deactivation mode.

The cylinder deactivation mode for each cylinder may be determined bymethod 2000 evaluating engine brake torque for all engine cylindersoperating in the first cylinder deactivation mode. If engine braketorque for operating the engine with all cylinders in the first cylinderdeactivation mode is greater than or equal to the desired engine braketorque, all engine cylinders are allowed to operate in the firstcylinder deactivation mode where intake valve and exhaust valves areheld closed as the engine rotates during an engine cycle. If the enginebrake torque for operating the engine with all cylinders in the firstcylinder deactivation mode is less than the desired engine brake torque,engine brake torque is determined for operating the engine with onecylinder in the second cylinder deactivation mode and three cylinders inthe first cylinder deactivation mode. If engine brake torque foroperating the engine with one cylinder in the second cylinderdeactivation mode and three cylinders in the first cylinder deactivationmode is greater than or equal to the desired engine brake torque, onecylinder is authorized to operate in the second cylinder deactivationmode and three cylinders are authorized to operate in the first cylinderdeactivation mode. Otherwise, engine torque for operating the enginewith two cylinders in the second cylinder deactivation mode and twocylinders in the first cylinder deactivation mode is determined. In thisway, one after the other, cylinder deactivation modes of each cylindermay be incremented from the first cylinder deactivation mode to thethird cylinder deactivation mode until the engine cylinder deactivationmodes that provide the desired engine brake torque are determined.

If the vehicle is not in tow/haul mode or hill descent mode, it may bedetermined to be in a fuel economy mode during deceleration conditions.As such, an actual number of engine cylinders with intake and exhaustvalves held closed during an engine cycle and not combusting air andfuel may be increased to improve vehicle coasting time and fuel economy.For example, all engine cylinders may be commanded with intake andexhaust valves held closed during an engine cycle. Method 2000 proceedsto 2050.

At 2050, method 2000 authorizes deactivation of the engine cylinders andtheir deactivation modes that provide the desired engine brake torque.Valves are authorized activated or deactivated according to the cylinderdeactivation modes and fuel is not injected to the cylinders so there isnot combustion in the cylinders in the deceleration fuel cut off mode.

At 2030, method 2000 judges if the vehicle is in a hill descent mode. Inone example, method 2000 judges that the vehicle is in hill descent modebased on an operating state of a pushbutton, switch, or variable inmemory. If method 2000 judges that the vehicle is in a hill descentmode, the answer is yes and method 2000 proceeds to 2032. Otherwise, theanswer is no and method 2000 proceeds to 2040.

In one example, the vehicle is controlled to a requested or desiredspeed when the accelerator pedal is not applied via controlling negativetorque produced via the engine and the vehicle brakes in hill descentmode. The vehicle may enter hill descent mode via releasing theaccelerator pedal. Further, engine braking may be controlled in hilldescent mode via adjusting engine valve timing. Further still,transmission gears may be shifted to provide a desired braking at thevehicle wheels via the engine.

At 2032 method 2000 determines a desired engine brake torque amount forcylinders not combusting air and fuel. In one example, the desiredengine brake torque amount may be empirically determined input to atable or function. The table or function may be specific to hill descentmode and different from the table or function for tow/haul mode. Thetable or function may be indexed via driver demand torque, vehiclespeed, and transmission gear. The table outputs the desired engine braketorque (e.g., negative torque the engine provides to the driveline todecelerate the vehicle driveline). Method 2000 proceeds to 2034 afterdetermining the desired engine brake torque.

At 2034, method 2000 shifts transmission gears according to a third gearshift schedule. The third transmission gear shift schedule up-shiftstransmission gears at higher engine speeds and higher vehicle speedsthan the first and second transmission gear shift schedules. The thirdtransmission gear shift schedule also downshifts transmission gears athigher engine speeds and higher vehicle speeds than the first and secondtransmission shift schedules to provide additional engine braking thanthe first and second transmission gear shift schedules. Method 2000proceeds to 2010 after shifting transmission gears according to thethird transmission shift schedule.

At 2040 method 2000 determines a desired engine brake torque amount forcylinders not combusting air and fuel. In one example, the desiredengine brake torque amount may be empirically determined input to atable or function. The table or function may be specific to fuel cut outmode not part of tow/haul mode or hill descent mode. The table orfunction may be indexed via driver demand torque, vehicle speed, andtransmission gear. The table outputs the desired engine brake torque(e.g., negative torque the engine provides to the driveline todecelerate the vehicle driveline). Method 2000 proceeds to 2042 afterdetermining the desired engine brake torque.

At 2042, method 2000 shifts transmission gears according to a first gearshift schedule. The first transmission gear shift schedule up-shiftstransmission gears at lower engine speeds and lower vehicle speeds thanthe second and third transmission gear shift schedules. The firsttransmission gear shift schedule also downshifts transmission gears atlower engine speeds and lower vehicle speeds than the second and thirdtransmission shift schedules to provide less engine braking than thesecond and third transmission gear shift schedules. Method 2000 proceedsto 2010 after shifting transmission gears according to the firsttransmission shift schedule.

In this way, cylinders may be operated in different modes where valvesmay be activated or deactivated to control engine braking while fuelflow to the engine cylinders is stopped. Different cylinders may beoperated in different modes to provide the desired engine brake torque.

Referring now to FIG. 21, a sequence for operating an engine accordingto the method of FIG. 20 is shown. The vertical lines at timeT2100-T2108 represent times of interest in the sequence. FIG. 21 showssix plots and the plots are time aligned and occur at the same time.

The first plot from the top of FIG. 21 is a plot of deceleration fuelcut off state versus time. The vertical axis represents the decelerationfuel cut off state. The engine is in deceleration fuel cut off mode whenthe trace is at a higher level near the vertical axis arrow. The engineis not in deceleration fuel cut off mode when the trace is at a lowerlevel near the horizontal axis. The horizontal axis represents time andtime increases from the left side of the figure to the right side of thefigure.

The second plot from the top of FIG. 21 is a plot of hill descent modestate versus time. The vertical axis represents hill descent mode stateand the vehicle is in hill descent mode when the trace is at a higherlevel near the vertical axis arrow. The vehicle is not in hill descentmode when the trace is at a lower level near the horizontal axis. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure.

The third plot from the top of FIG. 21 is a plot of tow/haul mode stateversus time. The vertical axis represents tow/haul mode state and thevehicle is in tow/haul mode when the trace is at a higher level near thevertical axis arrow. The vehicle is not in tow/haul mode when the traceis at a lower level near the horizontal axis. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The fourth plot from the top of FIG. 21 is a plot of transmission gearversus time. The vertical axis represents transmission gear andtransmission gears are indicated along the vertical axis. The horizontalaxis represents time and time increases from the left side of the figureto the right side of the figure.

The fifth plot from the top of FIG. 21 is a plot of cylinder poppetvalve state versus time. The vertical axis represents cylinder poppetvalve state. The poppet valve state may be active (e.g., poppet valvesopening and closing during an engine cycle), deactivated (e.g., poppetvalves not opening and closing during an engine cycle), partially active(PA) (e.g., intake valves held closed during an engine cycle and exhaustvalves opening and closing over the engine cycle). The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The sixth plot from the top of FIG. 21 is a plot of fuel injection stateversus time. The vertical axis represents fuel injection state and fuelinjection is activated when the trace is near the vertical axis arrow.Fuel injection is deactivated when the trace is near the horizontalaxis. The horizontal axis represents time and time increases from theleft side of the figure to the right side of the figure.

At time 2100, engine cylinders are active and cylinder valves areopening and closing over the engine cycle as the engine rotates andcombusts air and fuel since the poppet valves are active anddeceleration fuel cut out is not indicated. The vehicle is not in hilldescent mode nor is it in tow/haul mode. The vehicle's transmission isin third gear and all cylinder poppet valves are active (e.g., openingand closing over the engine cycle). Fuel injection is active and fuel isbeing supplied to the engine cylinders.

At 2101, the engine enters deceleration fuel cut off mode. The enginemay enter deceleration fuel cut off mode in response to a low driverdemand torque and vehicle speed greater than a threshold. The vehicle isnot in hill descent mode nor is it in tow/haul mode. The vehicle'stransmission is in third gear and all cylinder poppet valves aredeactivated (e.g., not opening and closing over the engine cycle). Thecylinder poppet valves are deactivated so that the engine cylinders arein a third cylinder deactivation mode in response to a low requestedengine brake torque (not shown). Further, exhaust gas or fresh air istrapped in the cylinder so that there is a spring effect on the piston.The closed intake and exhaust valves reduce engine pumping losses andmay extend the distance that the vehicle coasts. Closing the engine'sintake and exhaust valves also stops the engine from pumping fresh airto the catalyst in the engine's exhaust system so that the catalyst isnot cooled as much as if fresh air flowed to the catalyst. Further, theamount of oxygen stored in the catalyst is not increased so thatcatalyst efficiency may be high if the engine cylinders resumecombustion. Fuel injection is also ceased to the engine's cylinders sothat there is no combustion in the engine cylinders.

At time 2102, then engine exits deceleration fuel cut off mode and thecylinder's poppet valves are reactivated as indicated by the poppetvalve state trace. Fuel injection is also reactivated and combustionbegins in the engine cylinders. The engine may exit deceleration fuelcut off in response to an increase in driver demand torque or vehiclespeed being less than a threshold. The vehicle is not in hill descentmode nor is it in tow/haul mode. The vehicle's transmission is in thirdgear.

At time 2103, the vehicle enters hill descent mode. The vehicle mayenter hill descent mode via a driver applying a pushbutton or otherinput device. The vehicle is not in deceleration fuel cut off mode andit is not in tow/haul mode. The vehicle's transmission is in third gearand the cylinder's poppet valves are active. Fuel is also injected toengine cylinders and the engine combusts air and fuel.

At time 2104, the engine enters deceleration fuel cut off mode while inhill descent mode. The vehicle is not in tow/haul mode and thetransmission is in third gear. The cylinder's poppet valves arepartially deactivated (e.g., intake valves are held closed during anengine cycle and exhaust valves open and close during the engine cycle)in response to a middle level engine brake torque request while theengine rotates. Engine cylinders are in a second cylinder deactivationmode when the engine brake torque is at the middle level. However,engine cylinders may enter the first mode if the vehicle is acceleratingat a higher rate than is desired. Likewise, the engine cylinders mayenter the third cylinder deactivation mode if the vehicle isdecelerating faster than is desired. Fuel injection is deactivated sothat there is no combustion in engine cylinders.

At time 2105, the vehicle exits deceleration fuel cut off mode inresponse to increasing driver demand torque or vehicle speed being lessthan a threshold speed (not shown). The vehicle remains in hill descentmode and the transmission is in third gear. The vehicle is not intow/haul mode and the cylinder poppet valves are reactivated. Fuelinjection to engine cylinders is also reactivated so that the enginecylinders resume combusting air and fuel.

Between time 2105 and time 2106, the vehicle exits hill descent mode.The driver may request exiting hill descent mode via applying an inputto the vehicle or engine controller. The other engine/vehicle statesremain at their previous levels.

At time 2106, the vehicle enters tow/haul mode. The vehicle may entertow/haul mode via a driver applying a pushbutton or switch that providesinput to the vehicle or engine controller. The other engine/vehiclestates remain at their previous levels.

At time 2107, the engine enters deceleration fuel cut off mode inresponse to low driver demand torque and vehicle speed exceeding athreshold speed. The vehicle is also in tow/haul mode. The vehicle'stransmission is downshifted into second gear shortly after enteringdeceleration fuel cut off mode to increase engine braking via increasingengine speed (not shown). All engine cylinder poppet valves remainactive in response to a higher level engine brake torque request (notshown). Fuel injection is ceased to engine cylinders and the engine isnot combusting air and fuel as the engine rotates. Operating allcylinder valves while the engine throttle is closed (not shown)increases engine pumping losses and engine braking torque.

At 2108, the vehicle exits deceleration fuel cut off mode in response toan increase in driver demand torque or engine speed being reduced toless than a threshold. The vehicle remains in tow/haul mode and thecylinder poppet valves continue to be activated.

In this way, cylinder modes in which cylinder poppet valves are operatedin different ways may be used to vary engine braking torque so that adesired engine braking torque may be provided by the vehicle's engine.Further, some engine cylinders may be in a first operating mode whileother engine cylinders are in a second or third operating mode so thatthe desired engine braking torque may be provided.

Referring now to FIG. 22, a method for selecting a cylinder mode fromavailable cylinder modes is shown. The method of FIG. 22 may be includedin the system described in FIGS. 1A-6C. The method of FIG. 22 may beincluded as executable instructions stored in non-transitory memory. Themethod of FIG. 22 may perform in cooperation with system hardware andother methods described herein to transform an operating state of anengine or its components.

At 2202, method 2200 judges if basic conditions are present to enablecylinder modes where cylinders may be deactivated. Basic conditions mayinclude but are not limited to engine temperature being greater than athreshold, exhaust after treatment temperature greater than a threshold,battery start of charge greater than a threshold, and engine speedgreater than a threshold. Method 2200 verifies whether or not theconditions are present via monitoring various system sensors. If method2200 judges that basis conditions for cylinder deactivation or variabledisplacement engine operation are present, the answer is yes and method2200 proceeds to 2204. Otherwise, the answer is no and method 2200proceeds to 2220.

At 2220, method 2200 requests all engine cylinders are active andcombusting air and fuel Intake and exhaust valves of activated cylindersopen and close during an engine cycle so that air and combustionproducts flow through activated cylinders. Spark and fuel are alsoactivated so that fuel-air mixtures are combusted in activatedcylinders. Method 2200 proceeds to exit.

At 2204, method 2200 estimates noise, vibration, and harshness (NVH) inavailable cylinder modes. In one example, a noise table outputsempirically determined expected audible noise levels for theengine/vehicle. The noise table is indexed via the actual total numberof active engine cylinders, engine speed, and engine torque. A vibrationtable outputs empirically determined expected audible noise levels forthe engine/vehicle. The vibration table is indexed via the cylindermode, engine speed, and engine torque. Noise and vibration values areoutput for present engine speed, engine speed after a transmission gearshift, present driver demand torque, and driver demand torque after atransmission shift. Additionally, method 2200 may compare outputs ofvibration sensors (e.g., an engine knock sensor) and audible sensors tothreshold levels for the purpose of eliminating presently activecylinder deactivation modes that may not provide desired levels of noiseand vibration. Method 2200 proceeds to 2206.

At 2206, method 2200 evaluates noise and vibration outputs from thenoise and vibration tables, if the expected noise level of a tableoutput exceeds a threshold or if the expected vibration level of a tableoutput exceeds a threshold, the cylinder mode that provided the expectednoise and vibration is eliminated from presently available cylindermodes. For example, if expected engine noise for operating a fourcylinder engine in a second cylinder mode with two cylinder activecylinders at 2000 RPM exceeds a threshold at the present driver demandtorque or driver demand torque after a transmission shift, the secondcylinder mode at 2000 RPM is eliminated from a list of availablecylinder modes.

Alternatively, or additionally, method 2200 may compare noise andvibration sensor outputs to threshold levels. If engine noise exceeds athreshold in a presently activated cylinder mode, the presentlyactivated cylinder mode is eliminated from available cylinder modes sothat a cylinder mode that provides less engine noise may be selected.Likewise, if engine vibration exceeds a threshold in a presentlyactivated cylinder mode, the presently activated cylinder mode iseliminated from available cylinder modes so that a cylinder mode thatprovides less engine vibration may be selected.

Additionally, method 2200 may allow cylinder modes where expectedcylinder blow through (e.g., air flow from the engine's intake manifoldto the engine's exhaust manifold that does not participate incombustion) immediately following a cylinder mode change is expected tobe less than a threshold value. It may be desirable to avoid cylindermode changes where cylinder blow through is higher than the threshold toavoid disturbing oxygen in a catalyst downstream of the engine. Enginecylinder blow through amount may be determined according to U.S. patentapplication Ser. No. 13/293,015 filed Nov. 9, 2011, which is herebyfully incorporated by reference for all purposes. In one example, atable or function outputs an engine or cylinder blow through amountbased on cylinder mode, engine speed, and cylinder valve timing. Ifoutput from the table is less than the threshold amount, the cylindermode may be allowed. Method 2200 proceeds to 2208.

At 2208, method 2200 allows cylinder modes that are available and thathave not been eliminated from the available cylinder modes. Further,transmission gears that are available and that have not been eliminatedare allowed. Cylinder modes may be allowed so that they may eventuallybe selected for operating the engine at 716 of FIG. 7. A cylinder modewhere all engine cylinders are activated is always an allowed cylindermode unless engine or valve degradation is present. In one example, amatrix that includes cells representing cylinder modes is used to keeptrack of allowed and eliminated cylinder modes. Cylinder modes may beallowed by installing a value of one in cells that correspond toavailable cylinder modes. Cylinder modes may be eliminated by installinga value of zero in cells that correspond to cylinder modes that are notavailable or that are eliminated from engine operation. As previouslynoted, different cylinder modes may have a same number of actual totalactive cylinders while having different active cylinders. For example,if it is determined to be desirable to operate three cylinders of a fourcylinder engine to meet driver demand torque, cylinder mode numbersthree and four may be allowed where cylinder mode three has a firingorder of 1-3-2 and cylinder mode four has a firing order of 3-4-2. Inone engine cycle, cylinder mode three may be active. During a subsequentengine cycle, cylinder mode four may be active. In this way, the enginefiring order may be varied while maintaining an actual total number ofactive cylinders. Method 2200 proceeds to exit.

In this way, cylinder deactivation modes may be made available oreliminated may be identified. Further, basic conditions may have to bemet before available cylinder modes may be made allowable cylinder modesfor engine operation.

Referring now to FIG. 23, a method for controlling engine intakemanifold absolute pressure (MAP) during a deceleration fuel cut off modeis shown. The method of FIG. 23 may be included in the system describedin FIGS. 1A-6C. The method of FIG. 23 may be included as executableinstructions stored in non-transitory memory. The method of FIG. 23 mayperform in cooperation with system hardware and other methods describedherein to transform an operating state of an engine or its components.

At 2302, method 2300 judges if the engine is or should be indeceleration fuel cut off mode. In deceleration fuel cut off mode, oneor more engine cylinders, which may include all engine cylinders, may bedeactivated by stopping fuel flow to the cylinders. Further, gas flowthrough one or more cylinders may be stopped via deactivating intakevalves or intake and exhaust valves of a cylinder being deactivated inclosed positions as the engine rotates through an engine cycle. In oneexample, method 2300 judges that the engine should be in a decelerationfuel cut off mode when driver demand decreases from a higher value to alower value and vehicle speed is greater than a threshold speed. Ifmethod 2300 judges that the engine should be in deceleration fuel cutoff mode, the answer is yes and method 2300 proceeds to 2304. Otherwise,the answer is no and method 2000 proceeds to 2320.

At 2320, method 2300 operates the engine to provide a desired amount oftorque. The desired amount of torque may be a driver demand torque orbased on the driver demand torque. Valves of the engine are activated asrequested to provide the desired torque and the engine combusts air andfuel to provide the desired torque. Method 2300 proceeds to exit afterproviding the desired amount of torque.

At 2304, method 2300 determines a desired intake manifold pressure andan actual total number of cylinder intake valve opening events (e.g.,intake valves of each cylinder open once during an intake stroke of thecylinder with opening intake valves) or intake strokes of cylindersinducting air to reduce intake manifold pressure to a desired intakemanifold pressure. The actual total number of cylinder intake valveopening events may provide a better inference of intake manifoldpressure than time to pump the intake manifold pressure down. In oneexample, the methods described in U.S. Pat. Nos. 6,708,102 or 6,170,475,which are hereby fully incorporated for all purposes, may be used toestimate intake manifold pressure for a desired number of intake valveopening events or intake strokes into the future. For example, thethrottle may follow a predetermined trajectory from its current positionto a fully closed position in response to entering deceleration fuel cutoff mode. The predicted throttle position may be estimated from thepredetermined trajectory via the following equation:θ(k+1)=θ(k)+[θ(k)−θ(k−1)]where θ(k+1) is the estimate of throttle position at the next engineintake event; θ(k) is the measured throttle position at the presentengine intake event; and θ(k−1) is the measured throttle position at theprevious engine intake event.

The gas in the engine intake manifold is fresh air and the pressure inthe engine intake manifold is directly related to the cylinder aircharge. The throttle position, intake manifold pressure, intake manifoldtemperature, and engine speed are determined from the various enginesensors. To determine intake manifold pressure evolution, the startingpoint is a standard dynamic model governing the change of pressure inthe intake manifold as follows:

$P_{m} = {\frac{RT}{V}\left( {{M\; A\; F} - M_{cyl}} \right)}$where, T is the temperature in the intake manifold as sensed by intakemanifold temperature sensor, V is the volume of the intake manifold, Ris the specific gas constant, MAF is the mass flow rate into the intakemanifold and M_(cyl) is the flow rate into the cylinder The mass flowinto the cylinders (M_(cyl)) is represented as a near function of intakemanifold pressure with the slope and offset being dependent on enginespeed and ambient conditions as follows:

$M_{cyl} = {{{\alpha_{1}(N)}P_{m}} - {{\alpha_{2}(N)}\frac{P_{amb}}{P_{amb\_ nom}}}}$where P_(amb) and P_(amb) _(_) _(nom) are the current ambient pressureand the nominal value of the ambient pressure (e.g. 101 kPa). The enginepumping parameters α₁(N) and α₂(N) are regressed from the static enginemapping data obtained at nominal ambient conditions. After substitutingthis expression into the dynamic equation, for intake manifold pressureand differentiating both sides to obtain the rate of change of thepressure in the intake manifold, we obtain:

${\overset{¨}{P}}_{m} = {\frac{RT}{V}\left\lbrack {{\frac{d}{dt}M\; A\; F} - {\alpha_{1}{\overset{.}{P}}_{m}} - {{\overset{.}{\alpha}}_{1}P_{m}} - {{\overset{.}{\alpha}}_{2}\frac{P_{amb}}{P_{amb\_ nom}}}} \right\rbrack}$The dynamics governing change of engine speed are slower than the intakemanifold dynamics. A good tradeoff between performance and simplicity isto retain α₁(slope) and neglect α₂(offset). With this simplification,the second derivative of P_(m) is given by:

${\overset{¨}{P}}_{m} = {\frac{RT}{V}\left\lbrack {{\frac{d}{dt}M\; A\; F} - {\alpha_{1}{\overset{.}{P}}_{m}} - {{\overset{.}{\alpha}}_{1}P_{m}}} \right\rbrack}$To discretize the above equation, dP_(m)(k) is defined as a discreteversion of the time derivative of P_(m), that is dP_(m)(k)=(P_(m)(k+1)−P_(m)(k))/Δt, to obtain:

${{dP}_{m}\left( {k + 1} \right)} = \left( {1 - {\Delta\; t\;{\alpha_{1}\left( {{N(k)}\frac{RT}{V}} \right)}{dP}_{m}} + {\frac{RT}{V}\left\lbrack {{M\; A\;{F\left( {k + 1} \right)}} - {M\; A\;{F\left( {k - 1} \right)}}} \right\rbrack} - {{\frac{RT}{V}\left\lbrack {{\alpha_{1}\left( {N\left( {k + 1} \right)} \right)} - {\alpha_{1}\left( {N(k)} \right)}} \right\rbrack}{P_{m}(k)}}} \right.$Thus, this equation defines the predicted rate of change of the intakemanifold pressure one engine event into the future, which is used todetermine the future values of intake manifold pressure. However, attime instant k, the signals from the next (k+1) instant are notavailable. To implement the right hand side, instead of its value attime k+1, we use the one event ahead predicted value of the MAF signalat time k obtained by using, the one event ahead prediction of thethrottle position as follows:

${M\; A\;{F^{+ 1}(k)}} = {\frac{P_{amb}}{P_{amb\_ nom}}\sqrt{\frac{T_{amb\_ nom}}{T_{amb}}}{C\left( {\theta^{+ 1}(k)} \right)}{Fn\_ subsonic}\left( \frac{{P_{m}(k)} + {\Delta\;{{tdP}_{m}^{+ 1}\left( {k - 1} \right)}}}{P_{amb}} \right)}$where P_(amb) and P_(amb) _(_) _(nom) are current and nominal (i.e., 101kPa) absolute ambient pressures, T_(amb) and T_(amb) _(_) _(nom) arecurrent and nominal (i.e., 300 K) absolute ambient temperatures, andC(θ) is the throttle sonic flow characteristic obtained from staticengine data. Fn_subsonic is the standard subsonic flow correction:

${Fn}_{subsonic} = \begin{Bmatrix}\sqrt{14.96501\left\lbrack {\left( \frac{P_{m}}{P_{amb}} \right)^{1.42959} - \left( \frac{P_{m}}{P_{amb}} \right)^{1.7148}} \right\rbrack} & {{{if}\mspace{14mu}\frac{P_{m}}{P_{amb}}} \geq 0.52845} \\1.0 & {{{if}\mspace{14mu}\frac{P_{m}}{P_{amb}}} < 0.52845}\end{Bmatrix}$where P_(m)(k) is the current measurement of intake manifold pressure.For in-vehicle implementation the Fn_subsonic function can beimplemented as a tabulated lookup function of the pressure ratio. Inthis case, the magnitude of the slope should be invited to preventoscillatory behavior under wide open throttle conditions, possibly byextending the zero crossing of the function to a value of the pressureratio slightly over 1.

Several different choices are available to obtain the quantity MAF(k) tobe used in determining the future rate of change in the intake manifoldpressure. The following formula, which uses the previous value ofpredicted throttle position and current value of the manifold pressure,provides the best performance in terms of overshoot and stability atwide open throttle:

${M\; A\;{F(k)}} = {\frac{P_{amb}}{P_{amb\_ nom}}\sqrt{\frac{T_{amb\_ nom}}{T_{amb}}}{C\left( {\theta^{+ 1}\left( {k - 1} \right)} \right)}{Fn\_ subsonic}\left( \frac{P_{m}(k)}{P_{amb}} \right)}$To avoid predicting the engine speed, instead of subtracting the presentvalue of α₁ from its one, step ahead prediction, we approximate α₁ bysubtracting the one event old value from the present. The above changesresult in the dP_(m) signal corresponding to the one event aheadpredicted value of the time derivative of P_(m), i.e., the rate ofchange of the future intake manifold pressure:

${{dP}_{n}^{+ 1}(k)} = {{\left( {1 - {\Delta\; t\;{\alpha_{1}\left( {N(k)} \right)}\frac{RT}{V}}} \right){{dP}_{m}^{+ 1}\left( {k - 1} \right)}} + {\frac{RT}{V}\left\lbrack {{M\; A\;{F^{+ 1}(k)}} - {M\; A\;{F(k)}}} \right\rbrack} - {{\frac{RT}{V}\left\lbrack {{\alpha_{1}\left( {N(k)} \right)} - {\alpha_{1}\left( {N\left( {k - 1} \right)} \right)}} \right\rbrack}{P_{m}(k)}}}$Note that the value of dP_(m) ⁺¹(k) depends only on the signalsavailable at intake event k. Hence, it can be used in the prediction ofintake manifold pressure as follows:P _(m) ⁺¹(k)=P _(m)(k)+ΔtdP _(m) ⁺¹(k−1)P _(m) ⁺²(k)=P _(m)(k)+ΔtdP _(m) ⁺¹(k−1)+ΔtdP _(m) ⁺¹(k)where P_(m) ⁺¹(k) and P_(m) ⁺²(k) are one and two steps aheadpredictions of the intake manifold pressure. The manifold pressureevolution equations may be extended beyond two intake events into thefuture to a number of intake events that provides the desired intakemanifold pressure. In one example, the desired intake manifold pressureduring deceleration mode may be empirically determined and stored inmemory. For example he desired intake manifold pressure may beempirically determined and indexed in memory based on atmosphericpressure and vehicle speed. In one example, the desired engine intakemanifold pressure is a pressure in the intake manifold when the engineis operating at idle speed when driver demand torque is zero orsubstantially zero (e.g., less than 10 N-m. Further, the desired intakemanifold pressure may be adjusted responsive to ambient pressure. Forexample, if ambient pressure increases, desired intake manifold pressuremay be decreased. Method 2300 proceeds to 2306 after determining thedesired engine intake manifold pressure and the number of cylinderintake even s to achieve the desired intake manifold pressure.

At 2306, method 2300 fully closes the engine throttle and closes allengine intake events after the number of intake events determined at2304 to provide the desired intake manifold pressure has been performed.For example, if it is determined at 2304 that the desired intakemanifold pressure is 75 kPa and that the desired intake manifoldpressure may be reached as the throttle closes in four cylinder intakevalve opening events, intake valves of cylinders, and in some casesexhaust valves, are closed such that a total actual number of cylinderintake events after entering deceleration fuel cut off is four. In thisway, the cylinder valves are closed based on an actual total number ofintake valve opening events since a deceleration fuel cut off moderequest to provide a desired intake manifold pressure. Since thecylinder valves are closed, the engine may be started subsequentlywithout having to evacuate air from the intake manifold. Consequently,less fuel may be used to richen engine exhaust to improve catalystefficiency. Further the engine may be operated with less spark retardwhen reactivating cylinders since cylinder charge is less than a fullcharge. Method 2300 proceeds to 2308.

At 2308, method 2300 closes off the engine intake manifold to all vacuumconsumers. Vacuum consumers may include but are not limited to vacuumreservoirs; vehicle brakes; heating, ventilation, and cooling systems;and vacuum actuators such as turbocharger waste gates. However, ifvacuum in some systems (e.g., brakes) is reduced to less than athreshold, systems may again have access to the engine intake manifoldfor vacuum via opening a valve 176 as shown in FIG. 1B. Further, thevalves may be reactivated during such conditions so that the engine mayprovide additional vacuum to vacuum consumers. In one example, vacuumconsumers are provided selective access to engine intake manifoldpressure via one or more solenoid valves. Method 2300 proceeds to 2310.

At 2310, method 2300 operates a vacuum source to maintain engine intakemanifold pressure at the desired level. If air leaks by the throttle,intake manifold pressure may increase so that if the engine is restartedwith intake manifold pressure at atmospheric pressure, more fuel may beused to start the engine than is desired. Consequently, engine fuelconsumption may increase more than is desired if the engine is restartedwith a higher intake manifold pressure than is desired. Therefore, thevacuum source may be activated in response to intake manifold pressuregreater than the desired intake manifold pressure so that the intakemanifold pressure is less than atmospheric pressure (e.g., a vacuum isin the intake manifold). The vacuum source may be supplied electricalpower generated via the vehicle's kinetic energy or a battery.Additionally, the vacuum source may be activated to evacuate air from avacuum reservoir in response to low vacuum in the vacuum reservoir.Method 2300 proceeds to 2312.

At 2312, method 2300 ceases fuel flow and spark to engine cylinders. Airinducted during the intake events after the throttle begins to close,the intake events corresponding to the actual number of intake valveopening events determined at 2304, is combined with fuel and combustedbefore fuel and spark delivery to engine cylinders is ceased. Method2300 proceeds to 2314.

At 2314, method 2300 judges if conditions are present to exitdeceleration fuel cut off. In one example, deceleration fuel cut off maybe exited in response to a driver demand torque greater than a thresholdor vehicle speed less than a threshold. If method 2300 judges thatconditions are present to exit decoration fuel cut off mode, the answeris yes and method 2300 proceeds to 2316. The engine continues to rotateduring decoration fuel cut off since a portion of the vehicle's kineticenergy may be transferred to the engine. Otherwise, method 2300 returnsto 2310.

At 2316, method 2300 reactivates cylinder valves so that the valves openand close during an engine cycle. Further, fuel flow and spark deliveryare also provided to the cylinders. Combustion is resumed in thecylinders and the engine throttle position is adjusted to provide thedesired engine air flow and engine torque. The cylinder valve timing andthrottle positions may be empirically determined values stored in memoryindexed by engine speed and engine demand torque (e.g., driver demandtorque). Method 2300 proceeds to exit.

In this way, engine intake manifold pressure may be controlled toimprove cylinder reactivation and combustion in engine cylinders so thatfuel consumption may be reduced and catalyst balance (e.g., balancebetween hydrocarbons and oxygen in the catalyst) may be restored withless fuel being provided to the engine and/or catalyst.

Referring now to FIG. 24, a sequence for operating an engine accordingto the method of FIG. 23 is shown. The vertical lines at timeT2400-T2408 represent times of interest in the sequence. FIG. 24 showssix plots and the plots are time aligned and occur at the same time.

The first plot from the top of FIG. 24 is a plot of deceleration fuelcut off state versus time. The vertical axis represents the decelerationfuel cut off state. The engine is in deceleration fuel cut off mode whenthe trace is at a higher level near the vertical axis arrow. The engineis not in deceleration fuel cut off mode when the trace is at a lowerlevel near the horizontal axis. The horizontal axis represents time andtime increases from the left side of the figure to the right side of thefigure.

The second plot from the top of FIG. 24 is a plot of engine manifoldabsolute pressure (MAP) versus time. The vertical axis represents MAPand MAP increases in the direction of the vertical axis arrow. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure. Horizontal line 2402represents a desired MAP during deceleration fuel cut off mode.

The third plot from the top of FIG. 24 is a plot of engine throttleposition versus time. The vertical axis represents throttle position andthrottle position increases in the direction of the vertical axis arrow.The horizontal axis represents time and time increases from the leftside of the figure to the right side of the figure.

The fourth plot from the top of FIG. 24 is a plot of vacuum source stateversus time. The vertical axis represents vacuum source operating state(e.g., vacuum pump operating state) and the vacuum source is active whenthe trace is near the vertical axis arrow. The vacuum source is notactive when the trace is near the horizontal axis. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The fifth plot from the top of FIG. 24 is a plot of fuel delivery stateversus time. The vertical axis represents fuel delivery state and fuelis delivered to engine cylinders when the trace is near the verticalaxis arrow. Fuel is not delivered to engine cylinders when the trace isnear the horizontal axis. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

The sixth plot from the top of FIG. 24 is a plot of vacuum consumerstate versus time. The vertical axis represents vacuum consumer stateand the vacuum consumer state is active when the trace is near thevertical axis arrow. The vacuum consumers are not active when the traceis near the horizontal axis. Vacuum consumers are not in pneumaticcommunication with the engine intake manifold when the vacuum consumertrace is at a lower level. Vacuum consumers are in pneumaticcommunication with the engine intake manifold when the vacuum consumertrace is at a higher level. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

At time T2400, the engine is not in deceleration fuel cut off mode asindicated by the deceleration fuel cut off state being at a lower level.The engine MAP is relatively high indicating a higher engine load. Thethrottle position is open a large amount and the vacuum device state isoff to indicate that the vacuum source is not activated. Fuel is beingsupplied to engine cylinders as indicated by the fuel state being at ahigh level. The vacuum consumers are operating and able to consumevacuum based on the vacuum consumer state.

At time 2402, the engine transitions into deceleration fuel cut off modeas indicated by the desired fuel cut off state trace moving from a lowerlevel to a higher level. The engine may enter deceleration fuel cut offmode in response to a reduction in driver demand torque and vehiclespeed being greater than a threshold. The throttle is closed in responseto entering deceleration fuel cut off mode. Likewise, fuel flow is cutoff to engine cylinders as indicated by the fuel state trace being at alower level. The vacuum consumer state moves to a lower level toindicate that vacuum consumers are blocked from receiving vacuum fromthe engine intake manifold. By blocking air flow into the engine intakemanifold from vacuum consumers, intake manifold pressure may be reducedso that a large amount of fuel is not necessary to restart the enginewith stoichiometric air-fuel ratios in engine cylinders. Cylinder valvesare also closed in response to entering deceleration fuel cut off mode.A total actual number of intake valve opening events may be performed inresponse to entering deceleration fuel cut off mode before air flowthrough engine cylinders is ceased by closing cylinder intake valvesover one or more engine cycles while the engine continues to rotate. Thetotal actual number of intake valve opening events may be a number thatprovides a desired engine intake manifold pressure. In some examples,engine intake valves and exhaust valves may be closed over an enginecycle in response to entering deceleration fuel cut off mode.

Between 2402 and 2404, MAP is reduced and the engine remains indeceleration fuel cut off mode. MAP is reduced to a level of desired MAP2402. In one example, MAP is reduced to desired MAP 2402 by openingcylinder intake valves an actual total number of times based on anestimate of intake manifold pressure reaching 2402.

At 2404, MAP increases to a level above 2402 due to air leakage past theengine throttle or other air flow into the engine intake manifold. Thevacuum source is activated in response to the increased MAP so that MAPis lowered to 2402. The engine remains in deceleration fuel cut off modeand the throttle remains closed. The engine continues to rotate (notshown) and fuel flow to engine cylinders is stopped. Cylinder intakevalves remain deactivated and closed over each engine cycle (not shown).The vacuum source is deactivated shortly after being activated inresponse to MAP being less than 2402. The vacuum source state indicatesvacuum source activation (ON) and deactivation (OFF).

At 2406, MAP increases to a level above 2402 for a second time due toair leakage past the engine throttle or other air flow into the engineintake manifold. The vacuum source is activated in response to theincreased MAP so that MAP is lowered to 2402. The engine remains indeceleration fuel cut off mode and the throttle remains closed. Theengine continues to rotate (not shown) and fuel flow to engine cylindersis stopped. Cylinder intake valves remain deactivated and closed overeach engine cycle (not shown). The vacuum source is deactivated shortlyafter being activated in response to MAP being less than 2402. Thevacuum source state indicates vacuum source activation (ON) anddeactivation (OFF).

At time T2408, the engine exits deceleration fuel cut off mode whileintake manifold pressure is low. The engine may exit deceleration fuelcut off mode in response to an increase in driver demand torque. Thelower intake manifold pressure may reduce the use of spark retard andconserve fuel to reactivate engine cylinders and the catalyst in theengine exhaust system. The engine cylinders are reactivated by supplyingfuel to the cylinders and reactivating cylinder valves (not shown). Thevacuum consumers are also reactivated by allowing communication betweenthe vacuum consumers and the engine intake manifold. MAP increases asthe throttle is opened.

In this way, MAP may be controlled during deceleration fuel cut off modeto reduce fuel consumption. Further, driveline torque disturbances maybe reduced since the engine is started with a smaller air charge ascompared to if the engine is started with atmospheric pressure in theengine intake manifold.

Referring now to FIG. 25, a method for controlling engine intakemanifold absolute pressure (MAP) during cylinder reactivation afterentering a deceleration fuel cut off mode is shown. The method of FIG.25 may be included in the system described in FIGS. 1A-6C. The method ofFIG. 25 may be included as executable instructions stored innon-transitory memory. The method of FIG. 25 may perform in cooperationwith system hardware and other methods described herein to transform anoperating state of an engine or its components.

At 2502, method 2500 judge if cylinders and valves are deactivatedduring a deceleration fuel cut off mode. In one example, method 2500 mayjudge that engine cylinders are deactivated (e.g., not combusting airand fuel mixtures while the engine rotates) and valves are deactivated(e.g., held closed, not opening and closing as the engine rotates overan engine cycle) when a bit in memory is a predetermined value. Notethat all or only a fraction of engine cylinders may be deactivated. Ifmethod 2500 judges that engine cylinders and valves are deactivatedduring deceleration fuel cut off mode, the answer is yes and method 2500proceeds to 2504. Otherwise, the answer is no and method 2500 proceedsto 2540.

At 2540, method 2500 operates engine cylinders and valves to provide adesire torque. The desired torque may be based on accelerator pedalposition or a controller determined torque. The engine cylinders areactivated by supplying fuel to the cylinders. The valves are activatedby enabling valve operators. Further, volumetric efficiency actuatorsare adjusted to different positions than at 2508 for a same engine speedand torque demand to improve vehicle emissions and fuel economy. Method2500 proceeds to exit.

At 2504, method 2500 judges if cylinder reactivation is requested.Cylinder reactivation may be requested in response to an increase indriver demand torque or vehicle speed being less than a threshold speed.If method 2500 judges that cylinder reactivation is requested, theanswer is yes and method 2500 proceeds to 2506. Otherwise, method 2500proceeds to 2550.

At 2550, method 2500 maintains the cylinders in a deactivated state.Fuel is not supplied to the cylinders and the cylinder valves remaindeactivated. Method 2500 proceeds to exit.

At 2506, method 2500 judges if engine intake manifold pressure isgreater than a threshold pressure. If engine intake manifold pressure isgreater than a threshold pressure, the engine cylinders may produce moretorque than is desired or spark timing may be retarded to reduce enginetorque. If engine intake manifold pressure is greater than desired,cylinders may combust more fuel than is desired to providestoichiometric exhaust gases. Therefore, it may be desirable to reduceengine intake manifold pressure as soon as possible when reactivatingengine cylinders so that fuel may be conserved. If method 2500 judgesthat intake manifold pressure is greater than the threshold pressure,the answer is yes and method 2500 proceeds to 2508. Otherwise, theanswer is no and method 2500 proceeds to 2520. The threshold pressuremay vary with engine speed, vehicle speed, and ambient pressure.

At 2520, method 2500 adjusts engine volumetric efficiency actuators andthe engine throttle based on engine speed and driver demand torque. Inone example, driver demand torque is based on accelerator pedal positionand vehicle speed. The engine volumetric efficiency actuators mayinclude but are not limited to engine camshafts, charge motion controlvalves, and variable plenum volume valves. The positions of thevolumetric efficiency actuators may be empirically determined and storedto a table in memory that is indexed via driver demand torque and enginespeed. Different tables output different positions for the camshafts,charge motion control valves, and the variable plenum volume valves.Method 2500 proceeds to 2522.

At 2522, method 2500 reactivates engine cylinders and cylinder valves.The cylinders are reactivated by supplying spark and fuel to thecylinders. The cylinder poppet valves are reactivated by activatingvalve operators. The valve operators may be part of an assembly as shownin FIG. 5B, other valve operators described herein, or other known valveoperators. Activating the valve operator causes the intake valves toopen and close during an engine cycle. Method 2500 proceeds to exitafter activating the engine cylinders.

At 2508, method 2500 prepositions engine volumetric efficiency actuatorsto increase engine volumetric efficiency before engine cylinders andvalves are reactivated. The volumetric efficiency actuators arepositioned to increase engine volumetric efficiency at the engine'spresent speed and driver demand torque as compared to when thevolumetric efficiency actuators are adjusted responsive to engine speedand driver demand torque. In one example, cylinder charge motion controlvalves are fully opened to reduce resistance to flow entering enginecylinders. Further, intake valve timing and exhaust valve timing areadjusted via camshaft timing to provide no intake valve and exhaustvalve overlap (e.g., simultaneous opening of intake and exhaust valves).Further, intake valve timing may be advanced or retarded to maximize airin the cylinder at intake valve closing time. The variable plenum volumevalve is adjusted to minimize intake manifold volume. The enginethrottle is not adjusted when the engine volumetric efficiency actuatorsare adjusted. Engine boost may also be increased to increase enginevolumetric efficiency via closing a turbocharger waste gate or bypassvalve. Method 2500 proceeds to 2510 after engine volumetric efficiencyactuators are adjusted.

At 2510, method 2500 reactivates engine cylinders and cylinder valves.The cylinders are reactivated by supplying spark and fuel to thecylinders. The cylinder poppet valves are reactivated by activatingvalve operators. The valve operators may be part of an assembly as shownin FIG. 5B, other valve operators described herein, or other known valveoperators. Activating the valve operator causes the intake valves toopen and close during an engine cycle. Method 2500 proceeds to 2512after activating the engine cylinders.

At 2512, method 2500 judges if the engine intake manifold pressure is ata desired pressure. The desired pressure may be empirically determinedand based on engine speed and driver demand torque. If method 2500judges that engine intake manifold pressure is at the desired engineintake manifold pressure the answer is yes and method 2500 proceeds to2514. Otherwise, the answer is no and method 2500 returns to 2512.

At 2514, method 2500 positions engine volumetric efficiency actuatorsand the engine throttle based on engine speed and driver demand torque.The positions of the volumetric efficiency actuators may be empiricallydetermined and stored to a table in memory that is indexed via driverdemand torque and engine speed. Different tables output differentpositions for the camshafts, charge motion control valves, and thevariable plenum volume valves. Method 2500 proceeds to exit.

Referring now to FIG. 26, a sequence for operating an engine accordingto the method of FIG. 25 is shown. The vertical lines at timeT2600-T2405 represent times of interest in the sequence. FIG. 26 showssix plots and the plots are time aligned and occur at the same time.

The first plot from the top of FIG. 24 is a plot of cylinderdeactivation request versus time. The vertical axis represents thecylinder deactivation request. Cylinder deactivation is requested whenthe cylinder deactivation request trace is at a higher level near thevertical axis arrow. Cylinder deactivation is not requested when thecylinder deactivation request trace is at a lower level near thehorizontal axis. The horizontal axis represents time and time increasesfrom the left side of the figure to the right side of the figure.

The second plot from the top of FIG. 26 is a plot of cylinder stateversus time. The vertical axis represents the cylinder state. Thecylinder is deactivated when the cylinder state trace is at a lowerlevel near the horizontal axis. The cylinder is not deactivated when thecylinder trace is at a higher level near the vertical axis arrow. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure.

The third plot from the top of FIG. 26 is a plot of engine intakemanifold pressure versus time. The vertical axis represents engineintake manifold pressure and engine intake manifold pressure increasesin the direction of the vertical axis arrow. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure. Horizontal line 2602 represents a desiredengine intake manifold pressure during deceleration cut out. The levelof 2602 may be a same pressure as when the engine is operating at idlespeed and no driver demand torque.

The fourth plot from the top of FIG. 26 is a plot of engine volumetricefficiency actuator state versus time. The vertical axis representsengine volumetric efficiency actuator state and the engine volumetricefficiency actuator increases engine volumetric efficiency in thedirection of the vertical axis arrow. The engine volumetric efficiencyactuator state lowers engine volumetric efficiency when the trace isnear the horizontal axis. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

The fifth plot from the top of FIG. 26 is a plot of engine throttleposition versus time. The vertical axis represents engine throttleposition and the throttle opening amount increases when the trace iscloser to the vertical axis arrow. The engine throttle opening amountdecreases when the trace is near the horizontal axis. The horizontalaxis represents time and time increases from the left side of the figureto the right side of the figure.

The sixth plot from the top of FIG. 26 is a plot of driver demand torqueversus time. The vertical axis represents driver demand torque and thedriver demand torque increases in the direction of the vertical axisarrow. The driver demand torque decreases when the driver demand torquetrace is near the horizontal axis. The horizontal axis represents timeand time increases from the left side of the figure to the right side ofthe figure.

At time T2600, the cylinder deactivation request is not asserted and thecylinder state is asserted to indicate that engine cylinders are activeand combusting air and fuel. The engine intake manifold pressure is at ahigher level and the engine throttle position is open more than a middlelevel. The engine volumetric efficiency actuators (e.g., camshafts,charge motion control valves, and plenum control valve are at a middleposition to provide a middle level of engine volumetric efficiency. Thedriver demand torque is a middle level.

At time T2601, the cylinder deactivation request is asserted. Thecylinder deactivation request is asserted in response to a decrease indriver demand torque and the engine may be in deceleration fuel cut out.The engine throttle position is also decreased in response to thedecrease in driver demand torque. The cylinder state transitions to notasserted to indicate engine cylinders are deactivated in response to thecylinder deactivation request. The engine intake manifold pressuredecreases in response to closing the throttle. The cylinder intakevalves of cylinders are closed after the throttle closes and after anactual total number of cylinder intake events that reduced the intakemanifold pressure to desired level 2602. The cylinder exhaust valves mayalso be closed (not shown). The engine intake valves are held closedover one or more engine cycles when the cylinders are deactivated. Fuelflow to the cylinders is also deactivated (not shown). The position ofengine volumetric efficiency actuators remains unchanged.

Between time T2601 and time T2602, engine intake manifold pressure (MAP)increases in response to air leaking into the engine intake manifold.The air is not evacuated from the engine intake manifold since thecylinder intake valves are closed. The cylinder deactivation requestremains asserted and the cylinders remain deactivated. The throttleposition remains in a fully closed state and the driver demand remainslow.

At time T2602, the position of the engine volumetric efficiencyactuators is adjusted to increase engine volumetric efficiency ananticipation of reactivating engine cylinders. The engine volumetricefficiency actuators are not adjusted to positions based on engine speedand driver demand torque. Rather, they are adjusted to positions thatincrease engine volumetric efficiency beyond positions of enginevolumetric efficiency the actuators provide when they are adjustedresponsive to engine speed and driver demand torque. In this example,the position of volumetric efficiency actuators is adjusted in responseto engine intake manifold pressure exceeding a desired engine intakemanifold pressure 2602. By adjusting volumetric efficiency actuators inresponse to MAP, undesirable changes in the positions of the volumetricefficiency actuators may be avoided. Engine intake manifold pressureincreases from a pressure below 2602 to a pressure greater than 2602.However, the engine volumetric efficiency actuators may be adjusted apredetermined amount of time after deactivating cylinders or in responseto a request to reactivate engine cylinders. As an alternative, theengine volumetric efficiency actuator position may be adjusted toincrease engine volumetric efficiency in response to the request forcylinder deactivation. In one example, camshaft timing is advance orretarded to maximize air inducted from the engine intake manifold intoengine cylinders (e.g., camshaft timing is adjusted to provide a higherin cylinder pressure at the time of intake valve closing). Further,intake valve opening and exhaust valve opening overlap is adjusted tozero or negative to reduce air flow into the cylinder from the exhaustsystem (not shown). The engine throttle position and driver demandtorque remain unchanged.

At time T2603, the cylinder deactivation request is transitioned to notasserted in response to an increase in driver demand torque. Thecylinder deactivation request may transition to not asserted in responseto an increase in driver demand torque or vehicle speed being less thana threshold speed (not shown). Shortly thereafter, the engine cylindersare reactivated (e.g., intake and exhaust valves open and close eachengine cycle and spark and fuel are combusted within engine cylinders)as indicated by the cylinder state transitioning to indicate activecylinders. Further, the position of the volumetric efficiency actuatorsis adjusted to a position based on engine speed and driver demandtorque. The throttle position moves in response to the driver demandtorque.

Between time T2603 and time T2604, the driver demand torque increasesand then decreases. The throttle position also increases and decreasesin response to the driver demand torque. The engine intake manifoldpressure increases and then decreases to below 2602.

At time T2604, cylinder deactivation is requested a second time.However, because engine intake manifold pressure is below level 2602,the position of the volumetric efficiency actuators is not adjusted. Theengine cylinders are deactivated (e.g., combustion is inhibited in thecylinders via ceasing fuel flow and spark to the cylinders, cylindervalves are also deactivated so that they are held closed over one ormore engine cycles) as indicated by the cylinder state tracetransitioning to a lower level.

At time T2605, the cylinder deactivation request transitions to notasserted in response to vehicle speed less than a threshold (not shown).The engine cylinders are also reactivated as indicated by the cylinderstate trace transitioning to a higher level. The engine volumetricefficiency actuator positions are not adjusted responsive to thedeactivation request not being asserted because engine intake manifoldpressure is less than 2602.

In this way, MAP may be controlled when exiting a cylinder deactivationstate to conserve fuel and reduce torque disturbances. The volumetricefficiency actuators are adjusted to increase the amount of air inductedinto engine cylinders so that the engine intake manifold pressure isreduced soon after reactivating engine cylinders. Referring now to FIGS.27A and 27B, a method for controlling engine torque during cylindermodes is shown. The method of FIGS. 27A and 27B may be included in thesystem described in FIGS. 1A-6C. The method of FIGS. 27A and 27B may beincluded as executable instructions stored in non-transitory memory. Themethod of FIGS. 27A and 27B may perform in cooperation with systemhardware and other methods described herein to transform an operatingstate of an engine or its components.

At 2702, method 2700 judges if there is a request to decrease an actualtotal number of active cylinders (e.g., cylinders with valves that openand close during an engine cycle and cylinders that combust air and fuelduring the engine cycle). Method 2700 may judge that there is a requestto decrease an actual total number of actual cylinders in response to adecrease in driver demand torque, vehicle speed greater than athreshold, and/or other conditions. If method 2700 judges that there isa request to decrease an actual total number of active cylinders, theanswer is yes and method 2700 proceeds to 2704. Otherwise, the answer isno and method 2700 proceeds to 2714.

At 2704, method 2700 determines a desired lead of volumetric efficiencyactuators for decreasing an actual total number of active cylinders. Thelead for the volumetric efficiency actuators is an amount of time fromwhen positions of volumetric efficiency actuators are adjusted fordecreasing an actual total number of active cylinders to a time whendeactivation of cylinders begins. Adjusting the lead time for thevolumetric efficiency actuators may smooth engine torque and providetime for volumetric efficiency actuators to reach desired positionsbefore cylinder deactivation begins so that the engine does not providemore or less torque than is desired. In one example, the lead time isempirically determined and stored in memory. Further, the value of leadtime stored in memory may be adjusted based on a difference in desiredcylinder air charge and actual cylinder air charge during a transitionthat decreases the total actual number of active cylinders. The leadtime value is extracted from memory. Method 2700 proceeds to 2706.

At 2706, method 2700 prepositions the engine volumetric efficiencyactuators including an amount of boost provided by a turbocharger toincrease engine volumetric efficiency. For example, boost may beincreased, charge motion control valves may be fully opened, intakeplenum volume valves are positioned to decrease intake manifold volume,compressor bypass valves may be at least partially closed, and camshafttiming is adjusted to maximize cylinder charge at intake valve closingtime. Engine boost may be increased via closing a waste gate or closingthe compressor bypass valve. Adjusting the positions of enginevolumetric efficiency actuators increases the volumetric efficiency ofcylinders that remain active after the actual total number of activecylinders is decreased. Further, the engine's central throttle is atleast partially closed at the same time (e.g., simultaneously) as thepreviously mentioned engine volumetric efficiency actuators areadjusted. Closing the central throttle maintains the engine air flowrate while engine volumetric efficiency actuators are adjusted toincrease engine volumetric efficiency. Method 2700 proceeds to 2708.

At 2708, selected cylinders are deactivated after the lead time expires.The cylinders are deactivated via holding intake valves of the cylindersclosed over one or more engine cycles while the engine rotates. In someexamples, exhaust valves of the cylinders being deactivated may also beheld closed over one or more engine cycles while the engine rotates.Further, fuel flow and spark are not delivered to cylinders that arebeing deactivated. While cylinders are being deactivated, the centralthrottle is snapped open and fuel delivery is increased to activecylinders so that torque produced by active cylinders counters a torqueloss due to deactivating cylinders. Method 2700 proceeds to 2710.

At 2710, method 2700 adjusts spark timing in response to an errorbetween desired engine air flow and actual engine air flow. The desiredengine air flow is engine air flow based on driver demand torque at thetime of the cylinder deactivation request. The actual engine air flow isair flow that is measured via an air flow sensor. For example, if theactual engine air flow is greater than the desired engine air flow, theengine air flow error is negative and spark timing is retarded tomaintain engine torque. If the actual engine air flow is less than thedesired engine air flow, the engine air flow error is positive and sparktiming is advanced to maintain engine torque. Method 2700 proceeds to2712.

At 2712, method 2700 judges if engine volumetric efficiency actuatorsare at their desired positions. For example, method 2700 judges ifactual engine boost is equal to desired engine boost. Further, method2700 judges if actual camshaft timing is equal to desired camshafttiming. Likewise, method 2700 judge if actual charge motion controlvalve position is equal to desired charge motion control valve position.Method 2700 may judge that volumetric efficiency actuators are at theirdesired positions based on output of one or more sensors such as anintake manifold pressure sensor. If the engine volumetric efficiencyactuators are at their desired positions, the answer is yes and method2700 proceeds to 2714. Otherwise, the answer is no and method 2700returns to 2706 to provide more time to move the engine volumetricefficiency actuators.

At 2714, method 2700 adjusts the engine central throttle to provide adesired engine torque. The desired engine torque may be based on adriver demand torque. Method 2700 proceeds to 2720.

At 2720, method 2700 judges if there is a request to increase an actualtotal number of active cylinders (e.g., cylinders with valve that openand close during an engine cycle and cylinders that combust air and fuelduring the engine cycle). Method 2700 may judge that there is a requestto increase an actual total number of actual cylinders in response to anincrease in driver demand torque, vehicle speed less than a threshold,and/or other conditions. If method 2700 judges that there is a requestto increase an actual total number of active cylinders, the answer isyes and method 2700 proceeds to 2722. Otherwise, the answer is no andmethod 2700 proceeds to exit.

At 2722, prepositions the engine volumetric efficiency actuatorsincluding an amount of boost provided by a turbocharger to decreaseengine volumetric efficiency. For example, boost may be decreased,charge motion control valves may be at least partially closed, intakeplenum volume valves are positioned to increase intake manifold volume,and camshaft timing is adjusted to reduce cylinder charge at intakevalve closing time. Adjusting the positions of engine volumetricefficiency actuators decreases the volumetric efficiency of cylindersthat are active before the actual total number of active cylinders isincreased. Further, the engine's central throttle is at least partiallyopened at the same time (e.g., simultaneously) as the previouslymentioned engine volumetric efficiency actuators are adjusted. Openingthe central throttle maintains the engine air flow rate while enginevolumetric efficiency actuators are adjusted to decrease enginevolumetric efficiency.

Additionally, in some examples, intake valve and exhaust valve openingtime overlap of engine cylinders (e.g., activated and/or cylinders beingactivated) may be increased in response to turbocharger waste gateposition one cylinder cycle before cylinder reactivation. Theturbocharger waste gate position may be indicative of exhaust pressurein deactivated cylinders that include exhaust valves that open and closewhile the cylinder is deactivated. However, in other examples, theamount of overlap may be based on an amount of residual exhaust gas inthe cylinder. For example, the amount of overlap may be increased as theresidual amount of exhaust gas in the cylinder increases. If thedeactivated cylinders include non-deactivating exhaust valves, boostpressure may be decreased less as compared to if the cylinder isconfigured with deactivating exhaust valves because exhaust density incylinders with non-deactivating cylinders may be higher for otherwisesame conditions because exhaust in cylinders with non-deactivatingcylinders may be cooler. Method 2700 proceeds to 2724.

At 2724, selected cylinders are reactivated. The cylinders arereactivated via opening and closing intake valves of the cylinders overone or more engine cycles while the engine rotates. In some examples,exhaust valves of the cylinders being reactivated may also be opened andclosed over one or more engine cycles while the engine rotates. Further,fuel flow and spark are delivered to cylinders that are beingreactivated. While cylinders are being reactivated, the central throttleis snapped closed and fuel delivery is decreased to active cylinders sothat torque produced by active cylinders counters a torque increase dueto reactivating cylinders. Method 2700 proceeds to 2726.

At 2726, method 2700 adjusts spark timing in response to an errorbetween desired engine air flow and actual engine air flow. The desiredengine air flow is engine air flow based on driver demand torque at thetime of the cylinder deactivation request. For example, if the actualengine air flow is greater than the desired engine air flow, the engineair flow error is negative and spark timing is retarded to maintainengine torque. If the actual engine air flow is less than the desiredengine air flow, the engine air flow error is positive and spark timingis advanced to maintain engine torque. Method 2700 proceeds to 2728.

At 2728, method 2700 judges if engine volumetric efficiency actuatorsare at their desired positions. For example, method 2700 judges ifactual engine boost is equal to desired engine boost. Further, method2700 judges if actual camshaft timing is equal to desired camshafttiming. Likewise, method 2700 judge if actual charge motion controlvalve position is equal to desired charge motion control valve position.Method 2700 may judge that volumetric efficiency actuators are at theirdesired positions based on output of one or more sensors such as anintake manifold pressure sensor. If the engine volumetric efficiencyactuators are at their desired positions, the answer is yes and method2700 proceeds to 2714. Otherwise, the answer is no and method 2700returns to 2706 to provide more time to move the engine volumetricefficiency actuators.

At 2730, method 2700 adjusts the engine central throttle to provide adesired engine torque. The desired engine torque may be based on adriver demand torque. Method 2700 proceeds to exit.

In this way, positions of engine volumetric efficiency actuators may beadjusted when increasing and decreasing the actual total number ofactive cylinders. Moving the volumetric efficiency actuators at the sametime the engine central throttle is moved may reduce engine torquedisturbances and reduce engine fuel consumption.

Referring now to FIG. 28A, a sequence for operating an engine accordingto the method of FIGS. 27A and 27B is shown. The engine in the sequenceis a four cylinder engine having a firing order of 1-3-4-2. The verticallines at time T2800-T2804 represent times of interest in the sequence.FIG. 28A shows five plots and the plots are time aligned and occur atthe same time.

The first plot from the top of FIG. 28A is a plot of a desired number ofactive engine cylinders (e.g., cylinders with intake and exhaust valvesthat open and close during an engine cycle and cylinders in whichcombustion occurs) versus time. The vertical axis represents the desirednumber of active engine cylinders and the desired number of activecylinders is listed along the vertical axis. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The second plot from the top of FIG. 28A is a plot of an actual numberof active engine cylinders (e.g., cylinders with intake and exhaustvalves that open and close during an engine cycle and cylinders in whichcombustion occurs) versus time. The vertical axis represents the actualnumber of active engine cylinders and the actual number of activecylinders is listed along the vertical axis. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The third plot from the top of FIG. 28A is a plot of engine volumetricefficiency actuator position (e.g., waste gate position for adjustingengine boost, camshaft position, charge motion control valve position,plenum actuator position) versus time. The vertical axis representsengine volumetric efficiency actuator position and the position of theactuator increases engine volumetric efficiency in the direction of thevertical axis arrow. The position of the actuator decreases enginevolumetric efficiency near the horizontal axis. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The fourth plot from the top of FIG. 28A is a plot of central throttleposition versus time. The vertical axis represents central throttleposition and central throttle position increases in the direction of thevertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

The fifth plot from the top of FIG. 28A is a plot of spark timing versustime. The vertical axis represents spark timing and spark timingadvances in the direction of the vertical axis arrow. The spark timingis retarded near the horizontal axis. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

At time T2800, the desired actual total number of engine cylinders isfour and the actual total number of active cylinders is four. The enginevolumetric efficiency actuators are positioned to provide a lower levelof volumetric efficiency. For example, a waste gate is opened to reduceboost, cam timing is advanced to reduce cylinder charge, a plenum valveis positioned to increase intake manifold volume, and charge motioncontrol valves are closed to decrease volumetric efficiency. The enginethrottle is partially open and spark timing is advanced to a middlelevel.

At time 2801, the desired actual total number of active cylinderstransitions from four to two. The desired actual total number of activecylinders may be reduced in response to a reduction in driver demandtorque (not shown) or other conditions. The actual total number ofactive cylinders remains at a value of four since no cylinders have beendeactivated in response to the desired actual total number of activecylinders. The volumetric efficiency actuator position is providing alow level of engine volumetric efficiency and the throttle position isat a middle level. The spark timing is advanced to a middle level.

Between time T2801 and time T2802, the volumetric efficiency actuatorposition is changed to increase engine volumetric efficiency and thethrottle begins closing. The desired actual total number of activecylinders and the actual total number of active cylinders remainconstant. Spark timing also remains constant.

At time T2802, spark timing is retarded in response to an error betweenactual engine air flow being greater than desired engine air flow.Retarding spark timing truncates engine torque so that engine torque maybe maintained constant. The volumetric efficiency actuator positioncontinues to change to increase engine volumetric efficiency and thethrottle continues closing. The desired actual total number of activecylinders and the actual total number of active cylinders remainconstant.

At time T2803, deactivation of cylinder valves begins. The cylindervalves may be deactivated via valve operators described in FIG. 5B,other valve operators described herein, or other known valve operators.In one example, valve operators are deactivated to deactivate cylinderintake valves. Cylinder exhaust valves may also be deactivated. Thethrottle position is increased to open the throttle so that additionalair flows into the two cylinders that remain active. By increasingthrottle position, intake manifold pressure (MAP) increases, therebyincreasing air flow into active engine cylinders. Air flow ceases todeactivated cylinders as the intake valves of the cylinders beingdeactivated are deactivated and held closed. The spark timing begins tobe retarded since the air charge amount of active cylinders increases.The engine volumetric efficiency actuator does not change position andthe desired actual total number of active cylinders remains at a valueof two. The actual total number of active cylinders also remains at twosince engine cylinders have not been deactivated.

At time T2804, the actual total number of active engine cylinder changesfrom four to two. The intake valves of two cylinders (e.g., cylindernumbers 2 and 3) are deactivated (not shown) and the throttle positionremains constant. The spark timing ceases to change and the enginevolumetric efficiency actuator does not change position.

In this way, positions of volumetric efficiency actuators and the enginethrottle may be adjusted prior to deactivating cylinder valves so thatless fuel is used during cylinder mode transitions. Further, sparktiming may be adjusted responsive to cylinder air charge error insteadof in response to a change in engine throttle position so that lessspark retard may be used.

Referring now to FIG. 28B, a sequence for operating an engine accordingto the method of FIGS. 27A and 27B is shown. The engine in the sequenceis a four cylinder engine having a firing order of 1-3-4-2. The verticallines at time T2820-T2823 represent times of interest in the sequence.FIG. 28B shows five plots and the plots are time aligned and occur atthe same time.

The first plot from the top of FIG. 28B is a plot of a desired number ofactive engine cylinders (e.g., cylinders with intake and exhaust valvesthat open and close during an engine cycle and cylinders in whichcombustion occurs) versus time. The vertical axis represents the desirednumber of active engine cylinders and the desired number of activecylinders is listed along the vertical axis. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The second plot from the top of FIG. 28B is a plot of an actual numberof active engine cylinders (e.g., cylinders with intake and exhaustvalves that open and close during an engine cycle and cylinders in whichcombustion occurs) versus time. The vertical axis represents the actualnumber of active engine cylinders and the actual number of activecylinders is listed along the vertical axis. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The third plot from the top of FIG. 28B is a plot of engine volumetricefficiency actuator position (e.g., waste gate position for adjustingengine boost, camshaft position, charge motion control valve position,plenum actuator position) versus time. The vertical axis representsengine volumetric efficiency actuator position and the position of theactuator increases engine volumetric efficiency in the direction of thevertical axis arrow. The position of the actuator decreases enginevolumetric efficiency near the horizontal axis. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The fourth plot from the top of FIG. 28B is a plot of central throttleposition versus time. The vertical axis represents central throttleposition and central throttle position increases in the direction of thevertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

The fifth plot from the top of FIG. 28B is a plot of spark timing versustime. The vertical axis represents spark timing and spark timingadvances in the direction of the vertical axis arrow. The spark timingis retarded nearthe horizontal axis. The horizontal axis represents timeand time increases from the left side of the figure to the right side ofthe figure.

At time T2820, the desired actual total number of engine cylinders istwo and the actual total number of active cylinders is two. The enginevolumetric efficiency actuators are positioned to provide a higher levelof volumetric efficiency. For example, a waste gate is closed toincrease boost, cam timing is retarded to increase cylinder charge, aplenum valve is positioned to decrease intake manifold volume, andcharge motion control valves are opened to increase volumetricefficiency. The engine throttle is partially open and spark timing isadvanced to a lower middle level.

At time 2821, the desired actual total number of active cylinderstransitions from two to four. The desired actual total number of activecylinders may be increased in response to an increase in driver demandtorque (not shown) or other conditions. The actual total number ofactive cylinders remains at a value of two since no cylinders have beenreactivated in response to the desired actual total number of activecylinders. The volumetric efficiency actuator position is providing ahigher level of engine volumetric efficiency and the throttle positionis at a middle level. The spark timing is advanced to a lower middlelevel.

Between time T2821 and time T2822, the volumetric efficiency actuatorposition is changed to decrease engine volumetric efficiency and thethrottle begins opening. The desired actual total number of activecylinders and the actual total number of active cylinders remainconstant. Spark timing is constant.

At time T2822, reactivation of cylinder valves begins. The cylindervalves may be reactivated via valve operators described in FIG. 5B,other valve operators described herein, or other known valve operators.In one example, valve operators are reactivated to reactivate cylinderintake valves. Cylinder exhaust valves may also be reactivated. Thethrottle position is decreased to close the throttle so that less airflows into the two cylinders that are active. By decreasing throttleposition, intake manifold pressure (MAP) decreases, thereby decreasingair flow into active engine cylinders. Air flows into reactivatingcylinders as the intake valves of the cylinders being reactivated areopened and closed. The spark timing remains begins to be advanced sincethe air charge amount of active cylinders decreases. The enginevolumetric efficiency actuator does not change position and the desiredactual total number of active cylinders remains at a value of four. Theactual total number of active cylinders remains at two since enginecylinders have not been reactivated.

At time T2823, the actual total number of active engine cylinder changesfrom two to four. The intake valves of two cylinders (e.g., cylindernumbers 2 and 3) are reactivated (not shown) and the throttle positionremains constant. The spark timing ceases to change and the enginevolumetric efficiency actuator does not change position.

In this way, positions of volumetric efficiency actuators and the enginethrottle may be adjusted prior to reactivating cylinder valves so thatless fuel is used during cylinder mode transitions. Further, sparktiming may be adjusted responsive to cylinder air charge error insteadof in response to a change in engine throttle position so that lessspark retard may be used.

Referring now to FIG. 29, a method for controlling engine fuel injectionduring cylinder reactivation after entering a cylinder deactivation modeis shown. The method of FIG. 29 may be included in the system describedin FIGS. 1A-6C. The method of FIG. 29 may be included as executableinstructions stored in non-transitory memory. The method of FIG. 29 mayperform in cooperation with system hardware and other methods describedherein to transform an operating state of an engine or its components.

At 2902, method 2900 judges if one or more engine cylinders aredeactivated (e.g., intake valves held closed over an engine cycle as theengine rotates and no combustion in the deactivated cylinders). In oneexample, method 2900 may judge that one or more cylinders aredeactivated based on a value of a variable stored in memory or output ofone or more sensors. If method 2900 judges that one or more enginecylinders is deactivated, the answer is yes and method 2900 proceeds to2904. Otherwise, the answer is no and method 2900 proceeds to 2903.

At 2903, method 2900 operates engine cylinders and valves to provide adesire torque. The desired torque may be based on accelerator pedalposition or a controller determined torque. The engine cylinders areactivated by supplying fuel to the cylinders. The valves are activatedby enabling valve operators. Method 2900 proceeds to exit.

At 2904, method 2900 judges if cylinder reactivation is requested.Cylinder reactivation may be requested in response to an increase indriver demand torque or vehicle speed being less than a threshold speed.If method 2900 judges that cylinder reactivation is requested, theanswer is yes and method 2900 proceeds to 2906. Otherwise, method 2900proceeds to 2905.

At 2905, method 2900 maintains the cylinders in a deactivated state.Fuel is not supplied to the cylinders and the cylinder valves remaindeactivated. Method 2900 proceeds to exit.

At 2906, method 2900 judges if the engine is operating in a direct fuelinjection (DI) only region or if there is a change in requested enginetorque that is greater than a threshold. An engine with port and directfuel injectors may operate only the direct fuel injectors within a firstdefined engine operating range (e.g., a defined engine speed and torqueoutput range). Likewise, an engine with port and direct fuel injectorsmay operate only port fuel inject within a second defined engineoperating range. Further, in some engine operating ranges, fuel may besupplied to the engine via port and direct fuel injectors. Methoddetermines engine speed and engine torque then determines if the engineis operating in a range where only direct fuel injection is activated.If so, the answer is yes and method 2900 proceeds to 2908. Otherwise,the answer is no and method 2900 proceeds to 2920.

At 2920, method 2900 activates one or more deactivated engine cylindersby supplying spark and fuel to the deactivated cylinders. Additionally,valves of the deactivated cylinders that were held closed over one ormore engine cycles are activated to open and close over an engine cycle.The fuel is injected to the cylinders via port fuel injectors since theengine is not operating in a direct injection only engine operatingregion and since the rate of change in requested engine torque is lessthan the threshold. Method 2900 proceeds to exit after activating one ormore deactivated cylinders.

At 2908, method 2900 reactivates one or more engine cylinders viareactivating cylinder valves and supplying fuel and spark to thedeactivated cylinders. The engine cylinders are reactivated such thatvalves that were held closed during one or more engine cycles open andclose during one or more engine cycles. Fuel is supplied to the formerlydeactivated cylinders by directly injecting fuel to the cylinders.

Direct injection offers the opportunity to combust air and fuel in theformerly deactivated cylinders sooner than port injecting fuel becausedirect fuel injectors can inject fuel during a compression stroke of acylinder cycle (e.g., later in the cylinder cycle) while a port fuelinjector has to inject fuel during an intake stroke of the cylindercycle or earlier to support combustion during the cylinder cycle.Therefore, if cylinder reactivation is requested after an intake stokeof a cylinder, fuel can be injected during the compression stroke of thecylinder to support combustion in the cylinder during the compressionstroke. In this way, direct injection may enable combustion in adeactivated cylinder in less than 180 crankshaft degrees from thecrankshaft degree where cylinder activation is requested, whereas it maytake more than 180 crankshaft degrees from the crankshaft degree wherecylinder activation is requested for port fuel injected fuel injected toa formerly deactivated cylinder to participate in combustion.

If the engine is operating in a range where only port fuel is injectedto cylinders, except in engine cycles where the cylinders arereactivated, the cylinders may be reactivated by directly injecting fuelinto the cylinders for a predetermined number of engine cycles orcylinder intake events. Port fuel injection may be reactivated in thenewly reactivated cylinders after the predetermined number of enginecycles or cylinder intake events at which time direct fuel injection tothe newly reactivated cylinders ceases. In this way, the formerlydeactivated cylinders may start sooner and direct injection to thecylinders may cease after the predetermined number of engine cycles orcylinder intake events so that mixture preparation in the cylinders mayimprove soon after the cylinders are reactivated. This may beparticularly desirable during conditions where the rate of change inrequested engine torque is greater than a threshold so that the drivermay experience faster torque response to driver demand torque.

If the engine is operating in a region where only direct injection isprovided to engine cylinders, direct injection is resumed to thedeactivated cylinders and the cylinders operate with improved chargecooling. Direct fuel injection may continue in the engine cylindersuntil engine operating conditions change. Method 2900 proceeds to 2910.

At 2910, method 2900 judges if it is permissible to port inject fuel orif only direct fuel injection (DI) is desired. Port fuel injection maybe started after a predetermined actual total number of cylinder intakeevents since the request to activate one or more cylinders. Thepredetermined actual total number of events ensures that fuel is timelyinjected to formerly deactivated cylinders via direct fuel injection andthat fuel mixture preparation improves in a timely manner afterdeactivated cylinders are reactivated. Alternatively, only direct fuelinjection may be desired at the present engine operating conditions. Ifmethod 2900 judges that it is permissible to port fuel inject fuel or ifonly direct fuel injection is desired, the answer is yes and method 2900proceeds to 2912. Otherwise, method 2900 returns to 2908.

At 2912, method 2900 operates direct and port fuel injectors accordingto a base schedule. The base schedule may be based on engine speed anddriver demand torque. Therefore, direct fuel injection may be used toreactivate deactivated at earlier crankshaft angles after the request toactivate cylinders, then port fuel injection or port fuel injection anddirect fuel injection may replace only directly injecting fuel. Method2900 proceeds to exit.

Referring now to FIG. 30, a sequence for operating an engine accordingto the method of FIG. 29 is shown. The vertical lines at timeT3000-T3002 represent times of interest in the sequence. FIG. 30 showsthree plots and the plots are time aligned and occur at the same time.The SS marks along each plot represent a brake in time. The brake intime may be long or short in duration. Events to the left of the SSmarks represent engine operating conditions where fuel is only portinjected unless engine cylinders are being reactivated. Events to theright of the SS marks represent engine operating conditions where fuelis only directly injected. The sequence of FIG. 30 is for a fourcylinder engine with a firing order of 1-3-4-2. The three plots arealigned by crankshaft position.

Example exhaust valve opening times are indicated by the cross hatchedpatterns 3002, 3012, 3023, 3028, 3051, 3056, 3064, and 3069. Exampleintake valve opening time are indicated by the hatched patterns 3004,3013, 3024, 3029, 3052, 3057, 3065, and 3070. Start of direct fuelinjection events are indicated by nozzles 3006, 3053, 3058, 3062, and3066. Spark events are indicated by the * at 3010, 3015, 3026, 3054,3059, 3063, and 3067. Start of port fuel injection events are indicatedby nozzles at 3008, 3014, 3021, and 3025.

The first plot from the top of FIG. 30 is a plot of engine events versusengine position for cylinder number three. Engine strokes are plottedalong the horizontal axis and indicated by the letters I, C, P, and E. Irepresents intake stroke. C represents compression stroke, P representspower or expansion stroke, and E represents exhaust stroke. Verticalbars separate each engine stroke and represent top-dead-center orbottom-dead-center of piston travel. Port fuel injection windows such as3001 and 3011 are identified as PFI. Fuel may be injected to a cylinderfor a cylinder cycle via port fuel injectors during the port fuelinjection window. Port injecting fuel outside of the port fuel injectionwindow delivers fuel into a different cylinder cycle. Direct fuelinjection to cylinders may be during intake and compression strokes.

The second plot from the top of FIG. 30 is a plot of engine eventsversus engine position for cylinder number two. Engine strokes areplotted along the horizontal axis and indicated by the letters I, C, P,and E. I represents intake stroke. C represents compression stroke, Prepresents power or expansion stroke, and E represents exhaust stroke.Vertical bars separate each engine stroke and represent top-dead-centeror bottom-dead-center of piston travel.

The third plot is a plot of a cylinder reactivation request state versusengine position. The vertical axis represents cylinder reactivationstate and cylinder reactivation is requested when the plot's trace isnear the height of the vertical axis arrow. The cylinder reactivationstate is not requesting cylinder reactivation when the plot's trace isnear the horizontal axis. In some examples, the cylinder reactivationrequest may be replaced by a requested number of active cylindersvariable.

At time T3000, cylinder numbers two and three are deactivated (e.g.,fuel is not injected to the cylinders and the intake and exhaust valvesof the cylinders are held in a closed state over an engine cycle) andthe cylinder reactivation request is not asserted. Consequently, fuel isnot injected to cylinder numbers two and three. Further, intake andexhaust valves of cylinder numbers two and three are held closed.Cylinder numbers one and four are combusting air and fuel mixtures (notshown) while the engine rotates.

At time T3001, a request is made to reactivate engine cylinders as isindicated by the cylinder reactivation request transitioning to a higherlevel. The cylinder reactivation request occurs half way through portfuel injection (PFI) window 3001 and it may be based on an increase indriver demand torque. Because the port fuel injector has to provideprecise smaller fuel amounts and larger fuel amounts, its flow rate issuch that it cannot provide enough fuel during port fuel injectionwindow 3001 to provide for a stoichiometric mixture in cylinder numberthree. Therefore, fuel is directly injected so that combustion may startin cylinder number three as soon as possible after the cylinderreactivation request. Fuel is directly injected after the first intakestroke after time T3001. The fuel injected at 3006 is combusted at 3010.

The cylinder reactivation request occurs at the end of port injectionwindow 3020 before deactivated intake and exhaust valves beginoperating. Port fuel injection begins at 3021 early in port fuelinjection window 3022 so that the port fuel injector of cylinder numbertwo has sufficient time to inject a fuel amount that produces astoichiometric mixture in cylinder number two. Fuel is not directlyinjected into cylinder number two because the cylinder reactivationrequest occurs too late in the compression stroke to directly inject adesired amount of fuel.

Fuel is port injected into cylinder number three for a second combustionevent in cylinder number three at 3008. Fuel is port injected early inport fuel injection window 3011 so that a stoichiometric mixture may beprovided in cylinder number three. The fuel injected at 3008 is inductedinto cylinder number three when the intake valve is open at 3013. Thesecond combustion event occurs in cylinder number three at 3015.

Fuel is port injected into cylinder number two for a second combustionevent in cylinder number two at 3025. Fuel is port injected early inport fuel injection window 3027 so that a stoichiometric mixture may beprovided in cylinder number two. The fuel injected at 3025 is inductedinto cylinder number two when the intake valve is open at 3029. Thesecond combustion event occurs in cylinder number three at 3026.

Cylinder numbers two and three are deactivated a second time between theSS marks and time T3002. Fuel is not injected at this time andcombustion does not occur in the cylinders. Cylinder numbers one andfour combust air and fuel while the engine rotates (not shown). Cylinderreactivation is not requested.

At time T3002, the cylinder reactivation request is asserted for asecond time. The cylinder reactivation request may be asserted inresponse to an increase in driver demand torque or other conditions. Theengine is operating at conditions where only direct fuel injection isscheduled. Because port fuel injection is not scheduled, the firstdirect injection since the cylinder reactivation request is at 3062.Fuel is injected during a compression stroke of cylinder number two andit combusts with air that is trapped in the cylinder when cylindernumber two was deactivated. The injected fuel is combusted at a firstcombustion event 3063 since the cylinder reactivation request at T3002.However, in some examples, exhaust may be trapped in cylinder number twoor air may leak by pistons if cylinder number two is deactivated for anextended period of time. During those conditions, the first direct fuelinjection into cylinder number two after the cylinder reactivationrequest would be at 3066 after fresh air is drawn into cylinder numbertwo.

A first direct injection for cylinder number three after time T3002occurs at 3053 after intake and exhaust valves are reactivated andopened at 3051 and 3052. The fuel injected at 3053 is combusted at 3054.

A second direct injection into cylinder number two is performed at 3066.Fuel injected at 3066 is combusted with air inducted at 3065. Spark at3067 initiates the second combustion event in cylinder number two sincethe cylinder reactivation request at T3002.

A second direct injection into cylinder number three is performed at3058. Fuel injected at 3058 is combusted with air inducted at 3057.Spark at 3059 initiates the second combustion event in cylinder numberthree since the cylinder reactivation request at T3002.

In this way, direct fuel injection may reduce an amount of time toreactivate engine cylinders that have been deactivated. Further, portfuel may be injected after the engine cylinders are reactivated withdirect injection to improve mixing in engine cylinders, thereby reducingengine emissions.

Referring now to FIG. 31, a method for controlling an engine oil pumpresponsive to cylinder mode is shown. The method of FIG. 31 may beincluded in the system described in FIGS. 1A-6C. The method of FIG. 31may be included as executable instructions stored in non-transitorymemory. The method of FIG. 31 may perform in cooperation with systemhardware and other methods described herein to transform an operatingstate of an engine or its components.

At 3102, method 3100 judges if there is a request to switch cylinderintake valves or intake valves and exhaust valves to a deactivatedstate. The request may be based on the method of FIG. 22. If method 3100judges that there is a request to switch cylinder poppet valves to adeactivated state, the answer is yes and method 3100 proceeds to 3104.Otherwise, method 3100 proceeds to 3120.

At 3104, method 3100 determines a minimum oil gallery pressure todeactivate cylinder poppet valves at the present engine operatingconditions. In one example, the engine intake and exhaust poppet valvesare normally active and are deactivated by supplying pressurized oil tovalve operators. The pressurized oil deactivates the intake and exhaustvalves so that the intake and exhaust valves are held closed over one ormore engine cycles. If the pressure of the oil is reduced, thedeactivated valves are reactivated so that they open and close over anengine cycle.

The minimum oil pressure to deactivate the cylinder poppet valves may beempirically determined based on parameters such as engine oiltemperature and engine speed. The minimum oil pressure to deactivate thecylinder poppet valves may be stored in a table or function in memorythat may be indexed via the parameters. Method 3100 indexes the table orfunction to determine the minimum oil pressure to deactivate cylinderpoppet valves at the present engine operating conditions and proceeds to3106.

At 3106, method 3100 determines a minimum oil pressure to lubricate theengine at the present engine operating conditions. The minimum oilpressure to lubricate the engine may be empirically determined based onparameters such as engine oil temperature, engine torque, and enginespeed. The minimum oil pressure to lubricate the engine may be stored ina table or function in memory that may be indexed via the parameters.Method 3100 indexes the table or function to determine the minimum oilpressure to lubricate the engine at the present engine operatingconditions and proceeds to 3108.

At 3108, method 3100 determines a minimum oil pressure to actuatevariable timing camshafts at the present engine operating conditions.The minimum oil pressure to actuate variable timing camshafts may beempirically determined based on parameters such as engine oiltemperature, engine torque, and engine speed. The minimum oil pressureto actuate variable timing camshafts may be stored in a table orfunction in memory that may be indexed via the parameters. Method 3100indexes the table or function to determine the minimum oil pressure toactuate variable timing camshafts at the present engine operatingconditions and proceeds to 3110.

At 3110, method 3100 determines a maximum oil pressure from the minimumoil pressures determined at 3104-3108 and adjusts actuators to providethe same value. For example, if the minimum poppet valve deactivationoil pressure is 100 kPa, the minimum oil pressure to lubricate theengine is 200 kPa, and the minimum oil pressure to adjust camshaftposition relative to crankshaft position is 150 kPa, the maximum oilpressure from the minimum oil pressures is 200 kPa. The oil pressuresupplied by the oil pump is commanded to 200 kPa. This resultant oilpressure command is the static oil pressure command. The oil pressuremay be adjusted via adjusting oil pump displacement, position of a dumpvalve, or oil flow through cooling jets. Method 3100 proceeds to 3110.

At 3112, method 3100 commands an increase in oil pressure in an oilgallery leading to cylinder poppet valve operators. The oil pressure maybe increased via increasing a pump displacement command, decreasing flowthrough an oil gallery dump valve, decreasing flow through pistoncooling jets, or increasing oil pump speed. The oil pressure command isincreased to a value higher than a value to maintain the valves in aclosed state so that the valves are deactivated quickly. This increasein oil pressure command is the dynamic command. The dynamic command maybe empirically determined and stored in a table or array that is indexedby engine speed and oil temperature. The dynamic command is relativelyshort in duration and the static command is longer in duration. In thisway, the oil pump pressure command may be comprised of a static commandand a dynamic command. Additionally, method 3100 may adjust oil pressureoutput from the oil pump responsive to oil quality. For example, if oilquality is high, oil pump pressure may be reduced based on improved oillubricating capacity of newer or higher quality oil. Further, method3100 may not activate cylinder cooling jets at a same time as activatingor deactivating cylinders via intake and exhaust valve operators. Method3100 proceeds to 3114.

At 3114, method 3100 reduces oil pressure in the oil gallery to thevalue determined at 3110, or the static oil pressure command, once it isdetermined that desired cylinder poppet valves are deactivated. Method3100 proceeds to 3116.

At 3116, method 3100 the cylinder poppet valves are moved to therequested state or held in their present state if there is not a requestto change the cylinder state. Method 3100 proceeds to exit.

At 3120 method 3100 judges if there is a request to switch cylinderintake valves or intake valves and exhaust valves to an activated state.The request may be based on driver demand torque and/or other vehicleoperating conditions. If method 3100 judges that there is a request toswitch cylinder poppet valves to an activated state, the answer is yesand method 3100 proceeds to 3122. Otherwise, method 3100 proceeds to3114.

At 3122, method 3100 decreases oil pressure in an oil gallery leading tocylinder poppet valve operators. The oil pressure may be decreased viadecreasing a pump displacement command, increasing flow through an oilgallery dump valve, increasing flow through piston cooling jets, ordecreasing oil pump speed. Method 3100 proceeds to 3114.

Referring now to FIG. 32, a sequence for operating an engine accordingto the method of FIG. 31 is shown. The vertical lines at timeT3200-T3204 represent times of interest in the sequence. FIG. 32 showssix plots and the plots are time aligned and occur at the same time.

The first plot from the top of FIG. 32 is a plot of a cylinderdeactivation request state versus time. The cylinder deactivationrequest is the basis for activating and deactivating cylinders. Further,cylinder valves may be activated and deactivated based the cylinderdeactivation request. The vertical axis represents the cylinderdeactivation request and cylinder deactivation is being requested whenthe trace is at a higher level near the vertical axis arrow. Cylinderdeactivation is not requested when the trace is at a lower level nearthe horizontal axis. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

The second plot from the top of FIG. 32 is a plot of cylinderdeactivation state versus time. The vertical axis represents cylinderdeactivation state and one or more engine cylinders are deactivated whenthe deactivation state trace is at a higher level near the vertical axisarrow. Cylinders are not deactivated when the trace is at a lower levelnear the horizontal axis. Fuel ceases to flow deactivated cylinders andintake and exhaust valves of deactivated cylinders are held closed overone or more engine cycles so that combustion does not occur indeactivated cylinders. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

The third plot from the top of FIG. 32 is a plot of engine oil pumpdisplacement command versus time. The vertical axis represents theengine oil pump displacement command and the value of the engine oilpump displacement command increase in the direction of the vertical axisarrow. The engine oil pump displacement command is the combined valuesof the static oil pressure command and the dynamic oil pressure command.The horizontal axis represents time and time increases from the leftside of the figure to the right side of the figure.

The fourth plot from the top of FIG. 32 is a plot of the static oilpressure demand versus time. The vertical axis represents the static oilpressure demand and the value of the static oil pressure demandincreases in the direction of the vertical axis arrow. The horizontalaxis represents time and time increases from the left side of the figureto the right side of the figure.

The fifth plot from the top of FIG. 32 is a plot of the dynamic oilpressure command versus time. The vertical axis represents the dynamicoil pressure command and the value of the dynamic oil pressure commandincreases in the direction of the vertical axis arrow. The horizontalaxis represents time and time increases from the left side of the figureto the right side of the figure.

The sixth plot from the top of FIG. 32 is a plot of the engine oilgallery pressure command versus time. The vertical axis represents theengine oil gallery pressure and the value of the engine oil gallerypressure command increases in the direction of the vertical axis arrow.The horizontal axis represents time and time increases from the leftside of the figure to the right side of the figure. Horizontal line 3202represents a minimum oil gallery pressure to hold a deactivated valve ina deactivated state.

At time T3200, the cylinder deactivation is not requested and cylindersare not deactivated. The static oil pressure command is at a lower leveland the oil pump displacement command is at a lower level. The dynamicoil pressure command is zero. The engine oil gallery pressure is at alower level.

At time T3202, the cylinder deactivation request is asserted. Thecylinder deactivation request may be asserted in response to a decreasein driver demand torque or other vehicle operating condition. Thecylinder deactivation state indicates that cylinders are notdeactivated. The dynamic oil pressure command is increased in responseto the cylinder deactivation request. The static oil pressure command isalso increased in response to the cylinder deactivation request. The oilpump displacement command increases in response to the cylinderdeactivation request. The oil pump displacement command adjusts oil pumpdisplacement. The oil gallery pressure increases in response to the oilpump displacement command.

Alternatively, an oil gallery dump valve may be at least partiallyclosed to increase oil gallery pressure as shown. Further, in someexamples, engine cooling jet flow may be reduced to increase oil gallerypressure as shown. Further still, in some examples, oil pump speed isincreased to increase oil gallery pressure as shown.

At time T3203, the cylinder deactivation state transitions to a higherlevel to indicate that cylinder valves are deactivated and held closedover one or more engine cycles. The cylinder deactivation state may bebased on output of one or more sensors (e.g., valve operator sensors,exhaust sensors, or other sensors). The oil pump displacement command isdecreasing and the dynamic oil pressure command is decreasing. Thestatic oil pressure command remains at is previous value. The oilgallery pressure levels off at an oil pressure slightly greater than3202 so that the valves may remain deactivated and oil pump energyconsumption may be reduced.

At time T3204, the cylinder reactivation request is asserted bytransitioning the cylinder deactivation state to a lower level. Thecylinder reactivation may be made in response to an increase in driverdemand torque or other vehicle operating condition. The cylinderdeactivation state indicates that cylinders are deactivated. The dynamicoil pressure command is reduced in response to the cylinder reactivationrequest. The static oil pressure command is also reduced in response tothe cylinder reactivation request. The oil pump displacement commanddecreases in response to the cylinder reactivation request. The oil pumpdisplacement command adjusts oil pump displacement. The oil gallerypressure decreases in response to the oil pump displacement command.

Alternatively, an oil gallery dump valve may be at least partiallyopened to decrease oil gallery pressure as shown. Further, in someexamples, engine cooling jet flow may be increased to decrease oilgallery pressure as shown. Further still, in some examples, oil pumpspeed is decreased to decrease oil gallery pressure as shown.

At time T3204, the cylinder deactivation state transitions to a lowerlevel to indicate that cylinder valves are reactivated and opened andclosed over one or more engine cycles. The cylinder reactivation statemay be based on output of one or more sensors (e.g., valve operatorsensors, exhaust sensors, or other sensors). The oil pump displacementcommand is increasing and the dynamic oil pressure command isincreasing. The static oil pressure command remains at is previousvalue. The oil gallery pressure levels off at value that corresponds toa maximum oil pressure of minimum oil pressure to lubricate the engine,minimum oil pressure to actuate camshafts at a desired rate.

In this way, cylinder and cylinder valve deactivation may be acceleratedwhile decreasing energy consumed by the oil pump. Further, the cylindervalves may be reactivated quickly by including a dynamic oil pressurecontrol command

Referring now to FIG. 33, a method for controlling engine knockresponsive to cylinder operating mode is shown. The method of FIG. 33may be included in the system described in FIGS. 1A-6C. The method ofFIG. 33 may be included as executable instructions stored innon-transitory memory. The method of FIG. 33 may perform in cooperationwith system hardware and other methods described herein to transform anoperating state of an engine or its components.

At 3302, method 3300 maps or assigns outputs of engine knock sensors toactive cylinders. Alternatively, method 3300 may map outputs of engineknock sensors based on a deactivated cylinder map. For example, for afour cylinder engine with a firing order of 1-3-4-2 and engine knocksensors positioned as shown in FIG. 2A, knock sensors may be mappedaccording to table 2.

TABLE 2 Cylinder Cylinder mode deactivation mode 1 2 3 4 5 6 7 FUEL 1, 21, 2 1 2 1 2 1 FUEL AND AIR 1, 2 1, 2 1, 2 1, 2 1, 2 2 1, 2Table 2 includes two cylinder deactivation modes. The first mode islabeled FUEL and it describes a mode where cylinders are deactivated viaceasing to supply fuel to the cylinders while intake and exhaust valvescontinue to open and close over an engine cycle. The second mode islabeled FUEL AND AIR and it describes a mode where cylinders aredeactivated via ceasing to supply fuel to the cylinders while intake andexhaust valves are held in a closed state over an engine cycle.

Cylinder modes are identified as 1, 2, 3, 4, 5, 6, and 7. Changesbetween the various modes may be based on time the engine operates in amode, amount of oil in deactivated cylinders, number of enginerevolutions in the mode, and other conditions described herein that maylead to mode changes between different cylinder modes. Mode 1 is wherecylinders 1-4 are active (e.g., combusting air and fuel while valvesopen and close over an engine cycle) and the engine rotates via torqueproduced via cylinders 1-4. Mode 2 is where cylinders 1 and 4 are activeand the engine rotates via torque produced via cylinders 1 and 4. Mode 3is where cylinders 1, 4, and 2 are active and the engine rotates viatorque produced via cylinders 1, 4, and 2. Mode 4 is where cylinders 1,3, and 4 are active and the engine rotates via torque produced viacylinders 1, 3, and 4. Mode 5 is where cylinders 3 and 2 are active andthe engine rotates via torque produced via cylinders 3 and 2. Mode 6 iswhere cylinders 3, 4, and 2 are active and the engine rotates via torqueproduced via cylinders 3, 4, and 2. Mode 7 is where cylinders 1, 3, and2 are active and the engine rotates via torque produced via cylinders 1,3, and 2. Alternatively, the cylinder modes may describe cylinders thatare deactivated.

In this example, the table cells are filled with values 1 and/or 2, butother values may be used. A value of one indicates a knock sensorpositioned near cylinder numbers 1 and 2 is selected for sampling anddetermining engine knock. A value of two indicates a knock sensorpositioned near cylinders numbered 3 and 4 is selected for sampling anddetermining engine knock. For example, when the engine is operating incylinder mode A with a FUEL cylinder deactivation mode, knock sensors 1and 2 are selected and sampled for determining engine knock in cylinders1-4. On the other hand, when the engine is operating in cylinder mode Fwith a FUEL AND AIR cylinder deactivation mode, knock sensor 2 is theonly knock sensor selected and sampled for determining engine knock incylinders 3, 4, and 2.

Table 2 shows that individual engine knock sensors may be assigned todetect knock in different cylinders for different cylinder modes anddifferent cylinder deactivation modes. One engine knock sensor mayprovide improved signal to noise in one cylinder mode and one cylinderdeactivation mode while a different knock sensor may provide improvedsignal to noise in the one cylinder mode and a second cylinderdeactivation mode. Further, engine knock thresholds may be adjustedresponsive to the knock sensor that is providing knock data according toknock sensor assignments. The engine knock sensor or sensors that areassigned to a particular cylinder mode and cylinder deactivation modeare sampled during an engine cycle for indications of knock in activecylinders. An engine knock sensor not assigned to a particular cylindermode and a cylinder deactivation mode is not sampled or the samplestaken for that knock sensor are not used to determined engine knockduring an engine cycle. In this way, engine knock sensors may be mappedto improve signal to noise ratios. Similar maps may be provided for sixand eight cylinder engines. Method 33 proceeds to 3304.

At 3304, method 3300 determines which engine cylinders are activated anddeactivated. In one example, the activated cylinders are determined asdescribed at 1118 of FIG. 11 which determines if conditions are presentfor deactivating one or more cylinders. In other examples, activecylinders may be identified values of variables at particular locationsin memory. The values of the variables may be revised each time acylinder is activated or deactivated. For example, a variable in memorymay indicate the operating state of cylinder number one. A value of onein the variable may indicate that cylinder number one is active while avalue of zero in the variable may indicate that cylinder number one isdeactivated. The operating state of each cylinder may be determined inthis way. Method 3300 proceeds to 3306.

At 3306, method 3300 determines which engine cylinders are deactivatedby ceasing fuel flow to the cylinders but not ceasing air flow to thecylinders. Method 3300 also determines which cylinders are deactivatedby ceasing fuel flow and air flow to the deactivated cylinders. In oneexample, the controller assigns each cylinder a variable in memory tokeep track of the cylinder's deactivation mode. A cylinder'sdeactivation mode is saved in controller memory when the cylinder isdeactivated. For example, a value of a variable is 1 when cylindernumber one is deactivated by ceasing fuel flow to the deactivatedcylinder number one but not ceasing air flow to the deactivated cylindernumber one. Conversely, the value of the variable is 0 when the cylindernumber one is deactivated by ceasing fuel flow and air flow to thedeactivated cylinder number one. A cylinder may be deactivated via anyof the methods and systems described herein. The values of the variablesmay be revised each time a cylinder deactivated.

In some examples, a table similar to table 2 may be constructed tooutput a threshold knock value based on the cylinder mode and cylinderdeactivation mode. Values in the table may be empirically determined andstored to the table. The table is indexed via the cylinder mode and thecylinder deactivation mode. The table outputs the threshold knock valuesthat knock sensor outputs are compared against. If knock sensor outputexceeds the threshold knock value, knock may be determined. Method 3300proceeds to 3308.

At 3308, method 3300 monitors selected knock sensors to determine engineknock. In particular, knock sensors are selected based on the map ofknock sensors described at 3302. The map of knock sensors is indexed viathe cylinder mode and the cylinder deactivation mode. The table outputsengine knock sensors that are sampled during an engine cycle for engineknock in the various cylinder modes and cylinder deactivation modes. Inone example, the knock sensors are monitored during specific crankshaftangular ranges for detecting knock in activated cylinders.

If knock sensor output exceeds a threshold level (e.g., the knockthreshold levels described at 3306), engine knock is indicated. In someexamples, the knock sensor output may be integrated and compared to thethreshold level. If the integrated knock sensor output is greater thanthe threshold, engine knock is indicated. Method 3300 proceeds to 3310.

At 3310, method 3300 adjusts an actuator in response to the indicationof knock. In one example, spark timing is retarded to reduce engineknock. Fuel injection start of injection timing may be retarded toreduce cylinder pressure and engine knock. Alternatively, the amount offuel injected may be increased. Further, cylinder air charge may bereduced in some instances to reduce the possibility of engine knock.Further still, the ratio of an amount of port fuel injected to an amountof directly injected fuel may be adjusted in response to engine knock.For example, the amount of directly injected fuel may be increased whilethe amount of port injected fuel may be decreased. Method 3300 proceedsto exit after the actuator is adjusted.

Thus, the method of FIG. 33 provides for a method for operating anengine, comprising: operating the engine with a first group ofcombusting cylinders in response to a first condition; operating theengine with a second group of combusting cylinders in response to asecond condition; adjusting spark timing of a cylinder in response to anindication of knock via a first group of sensors during the firstcondition; and adjusting spark timing of the cylinder in response to anindication of knock via a second group of sensors during the secondcondition. The method includes where the first condition is one or morecylinders deactivated via ceasing fuel flow and not air flow to the oneor more cylinders.

In one example, the method includes where the second condition is one ormore cylinders deactivated via ceasing fuel flow and air flow to the oneor more cylinders. The method further comprises switching betweencombusting air and fuel in the first group of combusting cylinders andcombusting air and fuel in the second group of combusting cylinderswhile engine speed and load are substantially constant. The methodincludes where the first condition is a first group of deactivatedcylinders being deactivated for a threshold number of engine rotations.The method also includes where the second condition is a second group ofdeactivated cylinders being deactivated for a threshold number of enginerotations.

The method of FIG. 33 also provides for a method for operating anengine, comprising:

adjusting spark supplied to a cylinder in response to output of a firstknock sensor when a first group of cylinders is deactivated via ceasingfuel flow and not air flow to the first group of cylinders; andadjusting spark supplied to the cylinder in response to output of asecond knock sensor when the first group of cylinders is deactivated viaceasing fuel flow and air flow to the cylinder. The method furthercomprises combusting air and fuel in a second group of cylinders inresponse to a driver demand torque at a first engine speed and load. Themethod further comprises combusting air and fuel in a third group ofcylinders in response to an actual total number of engine revolutionsthe first group of cylinders is deactivated. The method furthercomprises adjusting a ratio of direct injection fuel amount to portinjection fuel amount of the cylinder in response to output of the firstand second knock sensors.

In some examples, the method includes where the cylinder is active andcombusting air and fuel. The method includes where the second knocksensor is different than the first knock sensor, and where adjustingspark includes adjusting spark timing. The method further comprisesadjusting an engine knock threshold responsive to the first knock sensorbeing a basis for detecting knock in the cylinder. The method furthercomprises adjusting the engine knock threshold responsive to the secondknock sensor being the basis for detecting knock in the cylinder.

Referring now to FIG. 34, a sequence for operating an engine accordingto the method of FIG. 34 is shown. The vertical lines at timeT3400-T3407 represent times of interest in the sequence. FIG. 34 showssix plots and the plots are time aligned and occur at the same time. Thesequence of FIG. 34 represents a sequence for operating a four cylinderengine at a substantially constant speed and driver demand torque (e.g.,torque and speed change by less than 5%).

The first plot from the top of FIG. 34 is a plot of spark timing foractive cylinders (e.g., cylinders combusting air and fuel) versus time.The vertical axis represents spark timing for active cylinders and sparkis more advanced when the trace is at a higher level near the verticalaxis arrow. Spark is less advanced or retarded when the trace is at alower level near the horizontal axis. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

The second plot from the top of FIG. 34 is a plot of active cylindergroup versus time. The vertical axis represents active cylinder groupand the cylinder group is active when the trace is at the level of thecylinder group. In this example, there are two possible cylinder groupsA and B as indicated along the vertical axis. Group 1 indicatescylinders 1-4 are active and combusting air and fuel. Group 2 indicatescylinders 1 and 4 are active and combusting air and fuel. Cylinders 2and 3 are deactivated when group 3 is active. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The third plot from the top of FIG. 34 is a plot of cylinderdeactivation mode versus time. The vertical axis represents the cylinderdeactivation mode. Cylinders are not deactivated when the cylinderdeactivation trace is near the center of the vertical axis. Deactivatedcylinders are deactivated via ceasing to supply air and fuel to thedeactivated cylinders when trace is near the vertical axis arrow.Deactivated cylinders are deactivated via ceasing to supply fuel to thedeactivated cylinders while air flows through the deactivated cylinderswhen trace is near the horizontal axis. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

The fourth plot from the top of FIG. 34 is a plot that shows sampledknock sensors versus time. The vertical axis represents the knock sensorbeing sampled. A value of one indicates that only the first knock sensoris sampled. A value of two indicates that only the second knock sensoris sampled. Values 1 and 2 indicate that both first and second knocksensors are sampled. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

The fifth plot from the top of FIG. 34 is a plot of knock sensor outputamplitude versus time. The vertical axis represents knock sensoramplitude and knock sensor output increases in the direction of thevertical axis arrow. Solid line 3404 is output from the first knocksensor. Dashed line 3406 is output from the second knock sensor. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure. Dashed line 3402 representsa threshold level for comparing knock sensor output. If knock sensoroutput is greater than 3402, engine knock is indicated. The level of3402 is adjusted for cylinder group and cylinder deactivation mode.

The sixth plot from the top of FIG. 34 is a plot of indicated engineknock versus time. The vertical axis represents indicated engine knock.The horizontal axis represents time and time increases from the leftside of the figure to the right side of the figure. An engine actuatormay be adjusted responsive to indicated engine knock to reduce thepossibility of further engine knock.

At time T3400, cylinder group 1 is active and spark timing is moreadvanced. Cylinders are not deactivated so the cylinder deactivationmode indicates no deactivated cylinders. The sampled knock sensors are 1& 2 so that the first and second knock sensors are sampled to determineif engine knock is present. The outputs from the first and second knocksensors is less than threshold 3402 so engine knock is not indicated.

At time T3401, the active cylinder group switches to group 2. Two enginecylinders are deactivated under group 2 (e.g., cylinder numbers 2 and3). The active cylinder group may change in response to a decrease indriver demand torque or other changes in vehicle operating conditions(e.g., engine temperature reaching a threshold temperature). Sparktiming is retarded to reflect a higher load in the two active cylinderseven though driver demand torque has not changed (not shown). The twocylinders are deactivated via deactivating fuel flow cylinders. Fuelinjection is stopped to stop fuel flow to the two cylinders. Aircontinues to flow through the deactivated cylinders since the cylinderdeactivation mode is FUEL. The sampled knock sensors remain unchanged.The knock sensor threshold 3402 is reduced to a lower level sincebackground noise may be reduced since two engine cylinders are inactiveand combustion noise may be reduced. The outputs of the knock sensorsdoes not exceed threshold 3402 so engine knock is not indicated.

At time T3402, the active cylinder group switches back to group 1. Theactive cylinder group may change state in response to an increase indriver demand torque, a decrease in engine temperature, or anothercondition. The cylinder deactivation mode switches back to the centervalue to indicate no cylinders are deactivated. The sampled knocksensors remain unchanged. The knock sensor threshold increases back toits previous level and no engine knock is indicated since the knocksensor outputs are less than threshold 3402. Engine spark timing returnsto its previous value.

At time T3403, the active cylinder group switches again to group 2. Thetwo cylinders are deactivated via deactivating fuel and air to thecylinders. Fuel injection is stopped to stop fuel flow to the twocylinders and intake and exhaust valves of the two deactivated cylindersare held closed during an engine cycle to cease air flow to the twodeactivated cylinders. The sampled knock sensors remain unchanged. Theknock sensor threshold 3402 is reduced to a lowest level sincebackground noise may be reduced by lack of combustion in deactivatedcylinders and deactivating cylinder valves since valve impact isreduced. The outputs of the first and second knock sensors does notexceed threshold 3402 so engine knock is not indicated. Spark timing isretarded to reflect the increased load on the active cylinders tomaintain the driver demand torque.

At time T3404, output of the first knock sensor exceeds threshold 3402.Therefore, engine knock is indicated as shown in the sixth plot. Sparktiming is further retarded in response to the indication of engineknock. The active cylinder group remains 2 and cylinder air flow andfuel flow to deactivated cylinders remains stopped. The sampled knocksensors remain unchanged. The knock sensor output decreases in responseto the increased spark retard.

At time T3405, the active cylinder group switches back to group 1. Thecylinder deactivation mode switches back to the center value to indicateno cylinders are deactivated. The sampled knock sensors remainunchanged. The knock sensor threshold increases back to its initiallevel and no engine knock is indicated since the knock sensor outputsare less than threshold 3402.

At time T3406, the active cylinder group switches to group 3. Threecylinders (e.g., cylinders numbered 1, 4, and 2) are active in cylindergroup 3. The sampled knock sensors switches from 1 & 2 to 1. Therefore,the first knock sensor is the only knock sensor sampled when group 3 isactivated and cylinders are deactivated via ceasing fuel flow withoutceasing air flow to deactivated cylinders (e.g., FUEL as shown in table2). By switching the knock sensors sampled, the signal to noise ratiofor determining engine knock may be improved. Engine knock is notindicated since the first and second knock sensor output is less thanthreshold 3402.

At time T3407, the active cylinder group switches back to group 1. Thecylinder deactivation mode switches back to the center value to indicateno cylinders are deactivated. The knock sensor threshold increases backto its initial level and no engine knock is indicated since the outputsof the first and second knock sensors less than threshold 3402.

In this way, different knock sensors may be sampled in response to theactive cylinder group and cylinder deactivation mode. Further, thethreshold level that knock sensor outputs are compared to may change inresponse to cylinder mode and cylinder deactivation mode. The cylindermodes, knock sensors sampled, knock threshold levels, and cylindergroups are exemplary in nature and are not intended to limit the scopeor breadth of the disclosure.

Referring now to FIG. 35, a method for controlling engine knockresponsive to cylinder deactivation mode is shown. The method of FIG. 35may be included in the system described in FIGS. 1A-6C. The method ofFIG. 35 may be included as executable instructions stored innon-transitory memory. The method of FIG. 35 may perform in cooperationwith system hardware and other methods described herein to transform anoperating state of an engine or its components.

At 3502, method 3500 estimates temperatures of engine cylinders via amodel and/or counts an actual total number of engine cycles thedeactivated cylinders are deactivated. Temperatures of active anddeactivated cylinders are modeled. In one example, a steady statetemperature of a cylinder is determined at 3504 via the followingequation:CYLss=Cyl_temp_fn(N,L,Cyl_d_state)·AF_fn(afr)·Spk_fn(spkMBT)·EGR_fn(EGR)where CYLss is the estimate of steady state cylinder temperature (e.g.,temperature of a cylinder); Cyl_temp_fn is cylinder temperature as afunction of engine speed (N), engine load (L), and cylinder deactivationstate (CYL_d_state); AF_fn is a function that provides a real numbermultiplier for cylinder air/fuel ratio (afr); Spk_fn a function thatprovides a real number multiplier for cylinder spark based on sparkretard for MBT spark timing (spkMBT); and EGR_fn is a function thatprovides a real number multiplier for exhaust gas recirculationpercentage (EGR). CYL_d_state identifies if the cylinder is active andcombusting air and fuel or deactivated and not combusting air and fuelso that the output CYLss changes if the engine cylinder changes fromactivated to deactivated or vise-versa. The steady state temperature ofa cylinder is modified by a time constant to provide the cylindertemperature estimate via the following equation:

${CYL}_{tmp} = {{{CYL}_{0}e^{\frac{- t}{\tau}}} + {{CYLss}\left( {1 - e^{\frac{- t}{\tau}}} \right)}}$where CYL_(tmp) is the final estimated cylinder temperature, CYL₀ is theinitial cylinder temperature, t is time, and τ is a system timeconstant. In one example, τ is a function of air flow through thecylinder whose temperature is being estimated and engine temperature. Inparticular, air flows through the cylinder when fuel flow to thecylinder is deactivated and combustion in the cylinder ceases. The valueof τ increases as air flow through the cylinder decreases, and the valueof τ decreases as air flow through the cylinder increases. The value ofτ decreases as engine temperature increases and the value of τ increasesas engine temperature decreases. The value of CYL_(imp) approaches thevalue CYLss if the cylinder is not deactivated for a longer duration.Method 3500 proceeds to 3506.

At 3506, method 3500 counts an actual total number of engine cycles theone or more cylinders are deactivated and not combusting air and fuel.In one example, a counter counts the actual number of engine cycles theone or more cylinders are deactivated by counting an actual total numberof engine revolutions since the one or more cylinders were deactivatedand dividing the result by two since there are two engine revolutions inone engine cycle. The actual number of engine revolutions is determinedvia output of the engine crankshaft position sensor.

At 3508, method 3500 monitors all engine cylinders for knock. All enginecylinders may be monitored for knock via one or more engine knocksensors. Engine knock sensors may include but are not limited toaccelerometers, pressure sensors, and acoustic sensors. Knock forindividual cylinders may be monitored during predetermined crankshaftangular intervals or windows. Engine knock may be present when output ofa knock sensor exceeds a threshold value. Method 3500 proceeds to 3510.

At 3510, method 3500 reduces the possibility of knock in enginecylinders where knock is indicated. In one example, method 3500 reducesthe possibility of engine knock in cylinders where engine knock wasindicated at 3508 by retarding spark timing of cylinders where engineknock was indicated. In other examples, start of fuel injection timingmay be retarded. Method 3500 proceeds to 3512.

At 3512, method 3500 advances spark timing of cylinders in which sparktiming was retarded to reduce the possibility of engine knock. Sparktiming is advanced to improve engine fuel economy, engine emissions, andengine efficiency. Spark timing may be advanced up to a spark timinglimit (e.g., minimum spark advance for best engine torque (MBT)) fromthe retarded spark timing based on a base spark advance gain.

A spark advance gain for a cylinder may be based on the cylinder'stemperature estimated at 3504 and/or the counted number of cycles thecylinder was deactivated and the counted number of cylinder cycles thecylinder is activated since the cylinder was deactivated its last time.The base spark advance gain may be added to the retarded spark timing.In one example, the spark advance gain for a cylinder may be expressedas X degrees/second where the value of variable X is based on cylindertemperature. Thus, spark may be advanced from a retarded timing byadding the spark advance gain value to the retarded spark timing. Forexample, if MBT spark timing is 20 degrees before top-dead-center andthe spark timing is retarded to 10 crankshaft degrees beforetop-dead-center in response to engine knock, the spark advance gainadvances spark timing from 10 crankshaft before top-dead-center to 20crankshaft degrees before top-dead-center in one second, unless engineknock is indicated while advancing spark timing. In other examples, thespark advance gain may be a multiplier that increases or decreases abase spark timing. For example, the spark advance gain may be a realnumber that varies between 1 and 2 such that if a base spark timing is10 degrees before top-dead-center, spark timing may be advanced up to 20degrees before top-dead-center by multiplying the base spark timing bythe spark advance gain. In this way, spark timing may be advanced backto MBT spark timing to improve engine emissions, fuel economy, andperformance. Method 3500 proceeds to exit.

Alternatively, the spark gain may be a function of the counted number ofcycles the cylinder was deactivated and the counted number of cylindercycles the cylinder is activated since the cylinder was deactivated itslast time. For example, if the cylinder was deactivated for 10,000engine cycles and activated for 5 engine cycles before knock wasencountered in the cylinder, the spark gain may be a larger value (e.g.,2 deg/second). However, if the cylinder was deactivated for 500 enginecycles and activated for 5 cycles before knock was encountered in thecylinder, the spark gain may be a smaller value (e.g., 1 deg/second).

Thus, a rate at which spark may be advanced after retarding spark forengine knock may be adjusted responsive to temperatures of cylindersand/or a number of actual total engine cycles since one or morecylinders were deactivated. Consequently, the rate that spark isadvanced may be adjusted to reduce the possibility of engine knock whenadvancing spark. Yet, spark may be advanced at a rate that improvesengine efficiency, economy, and performance.

Referring now to FIG. 36, a sequence for operating an engine accordingto the method of FIG. 35 is shown. The vertical lines at timeT3600-T3606 represent times of interest in the sequence. FIG. 36 showsfive plots and the plots are time aligned and occur at the same time.The sequence of FIG. 36 represents a sequence for operating a fourcylinder engine at a constant speed and driver demand torque.

The first plot from the top of FIG. 36 is a plot of cylinder (e.g., acylinder that is not combusting fuel and air) temperature versus timefor operation of the cylinder being illustrated. The vertical axisrepresents cylinder temperature and cylinder temperature increases inthe direction of the vertical axis arrow. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

The second plot from the top of FIG. 36 is a plot of cylinder sparktiming versus time for operation of the cylinder being illustrated. Thevertical axis represents spark timing of the cylinder and the sparkadvance increases in the direction of the vertical axis arrow. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure.

The third plot from the top of FIG. 36 is a plot of cylinderdeactivation mode versus time for the cylinder being illustrated. Thevertical axis represents the cylinder deactivation mode. The cylinder isnot deactivated when the cylinder deactivation trace is near the centerof the vertical axis. The cylinder is deactivated via ceasing to supplyair and fuel to the cylinder when trace is near the vertical axis arrow.The cylinder is deactivated via ceasing to supply fuel to the cylinderwhile air flows through the cylinder when trace is near the horizontalaxis. The horizontal axis represents time and time increases from theleft side of the figure to the right side of the figure.

The fourth plot from the top of FIG. 36 is a plot of cylinder sparkadvance gain for the illustrated cylinder in crankshaft degrees persecond versus time. The vertical axis represents spark advance gain andspark advance gain increases in the direction of the vertical axisarrow. The horizontal axis represents time and time increases from theleft side of the figure to the right side of the figure.

The fifth plot from the top of FIG. 36 is a plot of indicated engineknock versus time. The vertical axis represents indication of engineknock and engine knock is indicated when the trace is at a level nearthe vertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

At time T3600, the cylinder temperature is high and cylinder's sparktiming is more advanced. The cylinder is not deactivated as indicated bythe cylinder deactivation mode trace being at a middle level. Thecylinder's spark gain is at a lower level and engine knock is notindicated.

At time T3601, the engine cylinder is deactivated via stopping fuel flowand air flow to the cylinder as indicted by the cylinder deactivationmode trace. Air flow is stopped to the deactivated cylinder by holdingintake and exhaust poppet valves of the cylinder closed during an enginecycle. Alternatively, intake valves of the deactivated cylinder may beheld closed while exhaust valves of deactivated cylinder open and closeduring an engine cycle. The temperature of the cylinder begins todecline, but at a lower rate since air is not flowing through thedeactivated cylinder. The cylinder spark advance gain remains unchangedwhile the cylinder is deactivated. Spark timing for the cylinder is notshown since the cylinder is deactivated. Engine knock is not indicated.

At time T3602, the cylinder is reactivated by supplying fuel and air tothe cylinder as indicated by the cylinder deactivation mode tracetransitioning to the middle level. The cylinder spark advance gainincreases based on the cylinder's temperature. The cylinder's sparktiming returns to an advance level and the cylinder's temperature beginsincreasing. Knock is not indicated.

At time T3603, engine knock is indicated and the cylinder's spark timingis retarded to mitigate the engine knock. The cylinder temperature isincreasing but at a level less than a long term stable level for thepresent engine speed and load. The cylinder is active and the cylinderspark advance gain is at an elevated level.

Between time T3603 and time T3604, the spark timing for the cylinder isincreased using the spark advance gain based on the cylinder'stemperature. Knock in the cylinder is not present as the cylinder'sspark advance increases. The spark advance increases at a predeterminedrate (e.g., 10 crankshaft degrees/second) so that engine efficiency,performance, and emission may be improved after cylinder spark timing isretarded in response to engine knock. The cylinder spark advance gain isdecreased after the cylinder has been activated and cylinder temperaturehas increased.

At time T3604, engine cylinder is deactivated a second time via stoppingfuel flow to the cylinder while air continues to flow through thedeactivated cylinder as indicted by the cylinder deactivation modetrace. The cylinder temperature is at a level it was at back at timeT3600 and then it begins to decline at a fast rate since air flowingthrough the cylinder cools the cylinder. Knock in the cylinder is notindicated because the cylinder is deactivated.

At time T3605, the cylinder is reactivated by supplying spark and fuelto the cylinder. The cylinder may be reactivated in response to anincrease in requested engine torque or other operating conditions. Thecylinder spark timing is at a more advanced value or timing. Thecylinder temperature begins to increase after the cylinder isreactivated. The cylinder spark advance gain is also increased inresponse to activating the cylinder. Knock is not indicated in thecylinder.

At time T3606, engine knock is indicated. The cylinder's temperature isat a lower level and when knock is indicated. Spark timing for thecylinder is retarded in response to knock in the cylinder. Thecylinder's temperature continues to increase.

After time T3606, the cylinder spark timing is advanced at apredetermined rate (e.g., 15 crankshaft degrees/second) so that engineefficiency, performance, and emission may be improved after activecylinder spark timing is retarded in response to engine knock. Thecylinder spark timing increases in a ramp-like fashion and it increasesat a faster rate than at time T3603. Spark timing may be increased at afaster rate since the cylinder temperature is lower than at time T3603.Engine knock is not indicated in the cylinder and the cylindertemperature continues to increase.

In this way, engine spark timing may be adjusted responsive to thecylinder deactivation mode and the cylinder spark advance gain. Further,engine knock may be mitigated while degradation of engine performanceand emissions is reduced.

Referring now to FIG. 37, a method for controlling engine knock in thepresence of cylinder deactivation is shown. The method of FIG. 37 may beincluded in the system described in FIGS. 1A-6C. The method of FIG. 37may be included as executable instructions stored in non-transitorymemory. The method of FIG. 37 may perform in cooperation with systemhardware and other methods described herein to transform an operatingstate of an engine or its components.

Referring now to 3702, method 3700 determines engine knock windows fordetecting knock in each engine cylinder. In one example, engine knockdetection windows are engine crankshaft intervals where engine knock isexpected to occur. For example, if top-dead-center compression strokefor cylinder number one is 0 crankshaft degrees, knock in cylindernumber on may be expected in a range of between 20 crankshaft degreesafter top-dead-center cylinder number one compression stroke and 50crankshaft degrees after top-dead-center cylinder number one compressionstroke. Thus, the knock detection for cylinder number one is between 20and 50 crankshaft degrees after top-dead-center cylinder number onecompression stroke in this example. Knock detection windows for otherengine cylinders may be defined similarly. The engine knock windowranges for each cylinder may be empirically determined and stored in atable or function in controller memory. The table may be indexed viaengine speed and engine torque. Method 3700 proceeds to 3704.

At 3704, method 3700 selectively samples one or more engine knock sensoroutputs based on the present engine position and the engine knockwindows. For example, method 3700 samples an engine knock sensor in arange of between 20 crankshaft degrees after top-dead-center cylindernumber one compression stroke and 50 crankshaft degrees aftertop-dead-center cylinder number one compression stroke to determineknock sensor output for the knock window of cylinder number one. Method3700 proceeds to 3706.

At 3706, method 3700 judges if there is a good signal to noise ratio forthe knock sensor output in the latest or present knock sensor window. Inone example, method 3700 may base the judgement on predetermined signalto noise ratios stored a table or function in controller memory. Thetable or function may be indexed according to the present cylinder knockwindow, engine speed, and engine torque. If method 3700 judges thatthere is a good signal to noise ratio, the answer is yes and method 3700proceeds to 3720. Otherwise, the answer is no and method 3700 proceedsto 3708.

At 3708, method 3700 judges if one or more engine cylinders aredeactivated. In one example, variables in memory contain values thatidentify deactivated cylinders. For example, a variable that representsthe operational state of cylinder number one may have a value of zero ifthe cylinder is deactivated and a value of one if the cylinder is activeand combusting fuel and air. If method 3700 judges that one or moreengine cylinders are deactivated, the answer is yes and method 3700proceeds to 3710. Otherwise, the answer is no and method 3700 proceedsto 3740.

At 3710, method 3700 judges if knock sensor output noise in the knockwindow at the present crankshaft angle (e.g., present knock window), orif, the knock sensor output noise during a knock window in which knocksensor output was just sampled (e.g., present knock window), isinfluenced by fuel and air based cylinder deactivation of a cylinder.For example, combustion events for eight cylinder engines are onlyninety crankshaft degrees apart. Therefore, for an eight cylinder enginewith a firing order of 1-3-7-2-6-5-4-8, combustion noise (e.g., valveclosing and block vibration induced via combustion pressure) fromcylinder number 6 may enter the knock window of cylinder number 5. Ifmethod 3700 is evaluating knock sensor noise in the knock window ofcylinder number five, and cylinder number five is deactivated viadeactivating fuel flow and air flow to cylinder number five, then method3700 may judge that fuel and air based cylinder deactivation influencesknock sensor noise in the cylinder number five knock window. Note thateven though in this example cylinder number five is deactivated, noisein its knock window may be used for processing knock sensor output whencylinder number five is active during conditions of a low signal tonoise ratio.

Alternatively, if method 3700 is evaluating knock sensor noise in theknock window of cylinder number five, cylinder number six is deactivatedvia deactivating fuel flow and air flow to cylinder number six, andnoise (e.g., noise of exhaust valves closing while intake valves areheld closed during a cylinder cycle or noise from compression andexpansion in the deactivated cylinder) from cylinder number six entersthe knock window of cylinder number five while cylinder number five isactive and combusting air and fuel, then method 3700 may judge that fueland air based cylinder deactivation influences knock sensor noise in thecylinder number five knock window. If method 3700 judges that knocksensor output noise in the knock window at the present crankshaft angle(e.g., present knock window), or if, the knock sensor output noiseduring a knock window in which knock sensor output was just sampled(e.g., present knock window), is influenced by fuel and air basedcylinder deactivation of a cylinder, the answer is yes and method 3700proceeds to 3742. Otherwise, the answer is no and method 3700 proceedsto 3712.

At 3712, method 3700 judges if knock sensor output noise in the knockwindow at the present crankshaft angle (e.g., present knock window), orif, the knock sensor output noise during a knock window in which knocksensor output was just sampled (e.g., present knock window), isinfluenced by fuel based cylinder deactivation of a cylinder. Forexample, if method 3700 is evaluating knock sensor noise in the knockwindow of cylinder number five, and cylinder number five is deactivatedvia deactivating fuel flow while air flows to cylinder number five, thenmethod 3700 may judge that fuel based cylinder deactivation influencesknock sensor noise (e.g., noise from opening and closing of valves ofcylinder numbers five and six and compression and expansion noise fromcylinder numbers five and six) in the cylinder number five knock window.

Alternatively, if method 3700 is evaluating knock sensor noise in theknock window of cylinder number five, cylinder number six is deactivatedvia deactivating fuel flow while air flows to cylinder number six, andnoise (e.g., noise of exhaust valves closing while intake valves areheld closed during a cylinder cycle or noise from compression andexpansion in the deactivated cylinder) from cylinder number six entersthe knock window of cylinder number five while cylinder number five isactive and combusting air and fuel, then method 3700 may judge that fuelbased cylinder deactivation influences knock sensor noise in thecylinder number five knock window. If method 3700 judges that knocksensor output noise in the knock window at the present crankshaft angle(e.g., present knock window), or if, the knock sensor output noiseduring a knock window in which knock sensor output was just sampled(e.g., present knock window), is influenced by fuel based cylinderdeactivation of a cylinder, the answer is yes and method 3700 proceedsto 3742. Otherwise, the answer is no and method 3700 proceeds to 3730.

At 3714, method 3700 band pass filters output from a knock sensorsampled during the present knock window. The band pass filter may be afirst order or higher order filter. An average of the filtered knocksensor data is taken to provide a second knock reference value. In someexamples, the second knock reference value may be determined duringconditions where knock is expected to not occur. For example, a secondknock reference value may be determined when spark timing is retardedthree crankshaft degrees before borderline spark timing. Further, secondknock reference values may be determined periodically (e.g., once forevery 1000 combustion events in a cylinder at a particular engine speedand torque) instead of every engine cycle. Method 3700 proceeds to 3716.

At 3716, method 3700 processes the knock sensor data taken in thepresent knock window based on the second knock reference to determine ifknock is present in the cylinder in which combustion occurred for thepresent knock window. In one example, the knock sensor data taken in thepresent knock window is integrated to provide an integrated knock value.The integrated knock value is then divided by the second knock referencevalue and the result is compared to a threshold value. If the result isgreater than the threshold value, knock is indicated for the cylinderassociated with the knock window. Otherwise, knock is not indicated.Knock may be indicated by changing a value of a variable in memory.Method 3700 proceeds to 3718.

At 3718, method 3700 adjusts an actuator to mitigate engine knock. Inone example, spark timing for the cylinder associated with the knockwindow is retarded. Additionally, or alternatively, air flow to thecylinder associated with the knock window may be reduced via adjustingvalve timing. In still other example, an air-fuel ratio of the cylinderassociated with the knock window may be enrichened via adjusting timingof a fuel injector. Method 3700 exits after taking actions to mitigateknock.

At 3720, method 3700 judges if one or more engine cylinders are beingreactivated. Method 3700 may judge that one or more engine cylinders arebeing reactivated or are requested to be reactivated based on one ormore variables in memory changing state. For example, a variable thatrepresents the operational state of cylinder number one may have a valueof zero if the cylinder is deactivated and the value may transition to avalue of one if the cylinder is being reactivated. If method 3700 judgesthat one or more engine cylinders are being reactivated, the answer isyes and method 3700 proceeds to 3722. Otherwise, the answer is no andmethod 3700 proceeds to 3724.

At 3722, method 3700 adjusts one or more knock reference values for thecylinders being reactivated to a predetermined value or values that theknock reference values had just before the cylinders being reactivatedwere deactivated. The predetermined value may be empirically determinedand stored to memory. The values that the knock reference values hadjust before the cylinders being reactivated were deactivated are storedto memory when cylinder deactivation is requested. Thus, knock referencevalues for knock windows of each cylinder at various engine speeds andtorques are stored to memory in response to cylinder deactivation andthe same knock reference values are retrieved from memory in response toactivating deactivated cylinders so that the knock reference values arereasonable for activated cylinder conditions instead of using knockreference values determined during cylinder deactivation. Retrieving theknock reference values from memory may improve knock detection whencylinders are reactivated. Method 3700 proceeds to 3724.

At 3724, method 3700 band pass filters output from a knock sensorsampled during the present knock window. The band pass filter may be afirst order or higher order filter. An average of the filtered knocksensor data is taken to provide a third knock reference value. In someexamples, the third knock reference value may be determined duringconditions where knock is expected to not occur. For example, a thirdknock reference value may be determined when spark timing is retardedthree crankshaft degrees before borderline spark timing. Further, thirdknock reference values may be determined periodically (e.g., once forevery 1000 combustion events in a cylinder at a particular engine speedand torque) instead of every engine cycle. The knock reference value maynot be revised to the third reference value until a predetermined amountof time or engine cycles has occurred since cylinder reactivation.Instead, the third knock reference value may be the knock referencevalue determined at 3722 until the predetermined conditions are met.Method 3700 proceeds to 3726.

At 3726, method 3700 processes the knock sensor data taken in thepresent knock window based on the third knock reference to determine ifknock is present in the cylinder in which combustion occurred for thepresent knock window. In one example, the knock sensor data taken in thepresent knock window is integrated to provide an integrated knock value.The integrated knock value is then divided by the third knock referencevalue and the result is compared to a threshold value. If the result isgreater than the threshold value, knock is indicated for the cylinderassociated with the knock window. Otherwise, knock is not indicated.Knock may be indicated by changing a value of a variable in memory.Method 3700 proceeds to 3718.

At 3730 and 3740, method 3700 band pass filters output from a knocksensor sampled during the present knock window. The band pass filter maybe a first order or higher order filter. An average of the filteredknock sensor data is taken to provide a fourth knock reference value. Insome examples, the fourth knock reference value may be determined duringconditions where knock is expected to not occur. For example, a fourthknock reference value may be determined when spark timing is retardedthree crankshaft degrees before borderline spark timing. Further, fourthknock reference values may be determined periodically (e.g., once forevery 1000 combustion events in a cylinder at a particular engine speedand torque) instead of every engine cycle. Method 3700 proceeds to 3746.

At 3746, method 3700 judges if the fourth knock reference value isgreater than a threshold. The threshold may be empirically determinedand stored to memory. If the further knock reference value is higherthan the threshold, the knock intensity value may be lowered because ofthe way knock intensity is determined. Therefore, to improve the signalto noise ratio of the knock sensor output, the first knock referencevalue (e.g., determined at 3742) or the second knock reference value(e.g., determined at 3714) may be selected to process knock sensor datainstead of the fourth knock reference value. If method 3700 judges thatthe fourth knock reference value is greater than the threshold, theanswer is yes and method 3700 proceeds to 3750. Otherwise, the answer isno and method 3700 proceeds to 3748.

At 3748, method 3700 processes the knock sensor data taken in thepresent knock window based on the fourth knock reference to determine ifknock is present in the cylinder in which combustion occurred for thepresent knock window. In one example, the knock sensor data taken in thepresent knock window is integrated to provide an integrated knock value.The integrated knock value is then divided by the fourth knock referencevalue and the result is compared to a threshold value. If the result isgreater than the threshold value, knock is indicated for the cylinderassociated with the knock window. Otherwise, knock is not indicated.Knock may be indicated by changing a value of a variable in memory.Method 3700 proceeds to 3718.

At 3750, method 3700 processes the knock sensor data taken in thepresent knock window based on the first or second knock referencedetermined for the present engine speed and torque, but with deactivatedcylinders, to determine if knock is present in the cylinder in whichcombustion occurred for the present knock window. The integrated knockvalue is then divided by the first or second knock reference value andthe result is compared to a threshold value. If the result is greaterthan the threshold value, knock is indicated for the cylinder associatedwith the knock window. Otherwise, knock is not indicated. Knock may beindicated by changing a value of a variable in memory. The first knockreference value may be used to determine engine knock during a firstcondition and the second knock reference may be used to determine engineknock during a second condition. For example, the first knock referencevalue may be used if engine valve closing noise is greater than athreshold. The second knock reference value may be used if engine valueclosing noise is less than the threshold. Method 3700 proceeds to 3718.

At 3742, method 3700 band pass filters output from a knock sensorsampled during the present knock window. The band pass filter may be afirst order or higher order filter. An average of the filtered knocksensor data is taken to provide a first knock reference value. In someexamples, the first knock reference value may be determined duringconditions where knock is expected to not occur. For example, a firstknock reference value may be determined when spark timing is retardedthree crankshaft degrees before borderline spark timing. Further, firstknock reference values may be determined periodically (e.g., once forevery 1000 combustion events in a cylinder at a particular engine speedand torque) instead of every engine cycle. Method 3700 proceeds to 3744.

At 3744, method 3700 processes the knock sensor data taken in thepresent knock window based on the first knock reference to determine ifknock is present in the cylinder in which combustion occurred for thepresent knock window. In one example, the knock sensor data taken in thepresent knock window is integrated to provide an integrated knock value.The integrated knock value is then divided by the first knock referencevalue and the result is compared to a threshold value. If the result isgreater than the threshold value, knock is indicated for the cylinderassociated with the knock window. Otherwise, knock is not indicated.Knock may be indicated by changing a value of a variable in memory.Method 3700 proceeds to 3718.

Method 3700 may be performed for each engine cylinder as the enginerotates through all the engine cylinder knock windows in an enginecycle. The examples in the description of method 3700 are exemplary innature and are not intended to limit the disclosure.

Additionally, knock control for deactivated cylinders may be suspendedby not updating variables and/or adjusting spark timing to deactivatedcylinders (e.g., not providing spark to deactivated cylinders). In oneexample, cylinders that are deactivated are indicated to an engine knockcontroller so that the knock controller does not have to continue toprocess knock sensor data for deactivated cylinders.

In this way, knock reference values may be adjusted responsive tocylinder deactivation modes and cylinder deactivation to improve signalto noise ratios and engine knock detection. Further, multiple knockreference values may be provided at a particular engine speed and torquebased on cylinder deactivation.

Referring now to FIG. 38, a sequence for operating an engine accordingto the method of FIG. 37 is shown. The vertical lines at timeT3800-T3804 represent times of interest in the sequence. FIG. 38 showsthree plots and the plots are time aligned and occur at the same time.The sequence of FIG. 38 represents a sequence for operating a fourcylinder engine at a constant speed and driver demand torque.

The first plot from the top of FIG. 38 is a plot of a knock referencevalue for cylinder number one versus time. The vertical axis representsthe knock reference value for cylinder number one and the knockreference value increases in the direction of the vertical axis arrow. Ahigher knock reference value indicates higher background engine noise(e.g., engine noise not caused by knock in the cylinder being evaluatedfor knock). The horizontal axis represents time and time increases fromthe left side of the figure to the right side of the figure. Thecylinder number one knock reference value may be based on a first,second, third, or further reference value depending on operatingconditions. Horizontal line 3802 represents a threshold level abovewhich the fourth knock reference value may not be selected.

The second plot from the top of FIG. 38 is a plot of a selected knockreference value for cylinder number one versus time. The vertical axisrepresents the selected knock reference value for cylinder number oneand the knock reference value increases in the direction of the verticalaxis arrow. The selected knock reference value may be based on a first,second, third, or fourth knock reference value. The four knock referencevalues are determined as described in FIG. 37 and the selected knockreference is based on the present vehicle conditions. The selectedreference value is the reference value used to process the knock sensorinformation sampled in the knock window to judge whether or not knock isindicated (e.g., at 3748 of FIG. 37). The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

The third plot from the top of FIG. 38 is a plot of cylinderdeactivation mode versus time. The vertical axis represents the cylinderdeactivation mode. Cylinders are not deactivated when the cylinderdeactivation trace is near the center of the vertical axis. Deactivatedcylinders are deactivated via ceasing to supply air and fuel to thedeactivated cylinders when trace is near the vertical axis arrow.Deactivated cylinders are deactivated via ceasing to supply fuel to thedeactivated cylinders while air flows through the deactivated cylinderswhen trace is near the horizontal axis. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure.

At time 3800, the cylinder number one knock reference value is a highermiddle value less than threshold 3802. The cylinder number one knockreference value is the third knock reference value (e.g., 3724 of FIG.37) because cylinders are not deactivated and the knock sensor signal tonoise ratio is low. Engine cylinders are not deactivated as indicated bythe deactivated cylinder state being at the middle level. The selectedknock reference mode is the value of the cylinder number one knockreference value since the cylinder number one knock reference value isless than threshold 3802.

At time 3801, the cylinder number one knock reference value changes to alower value less than threshold 3802. The cylinder number one knockreference value is the first knock reference value (e.g., 3742 of FIG.37) because cylinders are deactivated via fuel and air and because theknock sensor signal to noise ratio is low. Engine cylinders aredeactivated via air and fuel (e.g., fuel flow and air flow throughcylinder number one is ceased) as indicated by the deactivated cylinderstate being at the lower level. The selected knock reference mode is thevalue of the cylinder number one knock reference value since thecylinder number one knock reference value is less than threshold 3802.Since cylinders are deactivated at time T3801, and since the deactivatedcylinder affects noise in the cylinder number one knock window, thecylinder number one reference value is the first knock reference value(e.g., from 3742 of FIG. 37).

At time T3802, the cylinder number one knock reference value increasesin response to reactivating cylinders. The cylinder number one knockreference value is the third knock reference value (e.g., 3724 of FIG.37) because it was the value before cylinders were deactivated at timeT3801. Engine cylinders are reactivated via supplying air and fuel tocylinder number one as indicated by the deactivated cylinder state beingat the middle level. The selected knock reference value is adjusted tothe cylinder number one knock reference value before cylinders weredeactivated at time T3801. By using the knock reference value beforecylinders were deactivated, an improve knock reference value may beprovided since the knock reference value is based on active cylinders(e.g., the current engine operating state) and not deactivated cylinders(e.g., the former engine operating state).

At time 3803, the cylinder number one knock reference value changes to alower value less than threshold 3802. The cylinder number one knockreference value is the second knock reference value (e.g., 3714 of FIG.37) because cylinders are deactivated via fuel (e.g., fuel injection tothe cylinders ceases while air is flowing through the cylinders) andbecause the knock sensor signal to noise ratio is low. The selectedknock reference value is the value of the cylinder number one knockreference value since the cylinder number one knock reference value isless than threshold 3802. Since cylinders are deactivated at time T3803,and since the deactivated cylinder affects noise in the cylinder numberone knock window, the cylinder number one reference value is the secondknock reference value (e.g., from 3714 of FIG. 37).

At time T3804, the cylinder number one knock reference value increasesin response to reactivating cylinders. The cylinder number one knockreference value is the third knock reference value (e.g., 3724 of FIG.37) because it was the value before cylinders were deactivated at timeT3803. Engine cylinders are reactivated via supplying air and fuel tocylinder number one as indicated by the deactivated cylinder state beingat the middle level. The selected knock reference value is adjusted tothe cylinder number one knock reference value before cylinders weredeactivated at time T3803.

In this way, the knock reference values of the cylinders that are thebasis for determining the presence or absence of engine knock may beadjusted responsive to cylinder deactivation and cylinder deactivationmode.

Referring now to FIG. 39, a method for performing diagnostics of anengine is shown. The method of FIG. 39 may be included in the systemdescribed in FIGS. 1A-6C. The method of FIG. 39 may be included asexecutable instructions stored in non-transitory memory. The method ofFIG. 39 may perform in cooperation with system hardware and othermethods described herein to transform an operating state of an engine orits components.

At 3902, method 3900 monitors the operating states of engine intake andexhaust valves. In one example, the operating states of engine intakeand exhaust valves are monitored via pressure sensors in the enginecylinders, engine exhaust system, and/or in the engine intake system(e.g., in the engine intake manifold). Method 3900 proceeds to 3904.

At 3904, method 3900 judges if cylinder deactivation (e.g., ceasingcombustion in the cylinder or cylinders) is requested or if cylinderdeactivation is presently underway. Method 3900 may determines whichengine cylinders are activated (e.g., combusting air and fuel) anddeactivated as described at 1118 of FIG. 11 or active cylinders may beidentified values of variables at particular locations in memory. Thevalues of the variables may be revised each time a cylinder is activatedor deactivated. For example, a variable in memory may indicate theoperating state of cylinder number one. A value of one in the variablemay indicate that cylinder number one is active while a value of zero inthe variable may indicate that cylinder number one is deactivated. Theoperating state of each engine cylinder may be determined in this way. Arequest to deactivate cylinders may also be based on a value of avariable in memory. Cylinder activation requests and deactivationrequests may be commands issued by the controller. If method 3900 judgesthat one or more cylinders is deactivated or requested deactivated, theanswer is yes and method 3900 proceeds to 3906. Otherwise, the answer isno and method 3500 proceeds to 3930.

At 3906, method 3900 judges if one or more poppet valves of cylindersrequested deactivated are active after commanding the poppet valvedeactivated and providing sufficient time to deactivate the cylinders(e.g., one full engine cycle after the request was made). One or morepoppet valves may be determined to be active based on cylinder pressure,exhaust pressure, or intake pressure. Alternatively, sensors may beplaced on the individual valve operators to determine whether or notvalves continue to operate after being commanded deactivated. If method3900 judges that one or more poppet valves that were commandeddeactivated (e.g., held closed as the engine rotates during an enginecycle) continues to operate (e.g., open and close as the engine rotatesduring the engine cycle), the answer is yes and method 3900 proceeds to3908. Otherwise, the answer is no and method 3900 proceeds to 3920. Notethat method 3900 may wait a predetermined amount of time aftercommanding the one or more poppet valves deactivated before proceedingto 3908 to ensure the poppet valve condition is valid.

At 3908, method 3900 reactivates the cylinder or cylinders in which thepoppet valves continue to operate. The cylinder or cylinders arereactivated by activating the cylinder's poppet valves and supplyingfuel and spark to the cylinders. Activating the cylinder poppet valvesprovides air to the cylinder. The air and fuel are combusted in theactivated cylinder. Method 3900 proceeds to 3910.

At 3910, method 3900 removes the cylinder with one or more valves thatdid not deactivate from a list of cylinders that may be deactivated.Thus, method 3900 inhibits cylinder deactivation for the cylinder withvalves that did not deactivate when the valves were commanded to bedeactivated. Method 3900 proceeds to 3912.

At 3912, method 3900 deactivates an alternative cylinder to provide adesired number of deactivated cylinders. For example, if cylinder numbertwo of a four cylinder engine is requested to be deactivated, but valvesof cylinder number two do not deactivate while cylinder numbers one,three, and four are activated, cylinder number two is reactivated asdescribed at 3910 and cylinder number three is commanded deactivated. Inthis example, the desired number of deactivated cylinders is one and thenumber of desired active cylinders is three. In this way, the desirednumber of active and deactivated cylinders may be provided.Consequently, improved fuel economy may be maintained even in thepresence of valve operator degradation. Method 3900 proceeds to exit.

At 3920, method 3900 provides a desired amount of engine torque viaactive cylinders. The desired amount of engine torque may be based on adriver demand torque, and the driver demand torque may be based on aposition of an accelerator pedal and vehicle speed. The desired amountof torque from the active cylinders is provided by controlling air flowand fuel flow to the active cylinders. Method 3900 proceeds to exit.

At 3930, method 3900 judges if one or more poppet valves of cylindersrequested activated or activated cylinders are deactivated aftercommanding the poppet valve activated and providing sufficient time toactivate the cylinders (e.g., one full engine cycle after the requestwas made). One or more poppet valves may be determined to be deactivatedbased on cylinder pressure, exhaust pressure, or intake pressure.Alternatively, sensors may be placed on the individual valve operatorsto determine whether or not valves do not open and close during anengine cycle after being commanded activated. If method 3900 judges thatone or more poppet valves that were commanded activated (e.g., open andclose as the engine rotates during an engine cycle) do not open andclose during the engine cycle, the answer is yes and method 3900proceeds to 3932. Otherwise, the answer is no and method 3900 proceedsto 3940. Note that method 3900 may wait a predetermined amount of timebefore proceeding to 3932 after commanding the one or more poppet valvesactivated to ensure the poppet valve condition is valid.

At 3932, method 3900 deactivates the cylinder or cylinders in which thepoppet valves do not open and close during a cylinder cycle. Thecylinder or cylinders are deactivated by deactivating the cylinder'spoppet valves and ceasing the supply of fuel and spark to the cylinders.Deactivating the cylinder poppet valves ceases air flow to the cylinder.Method 3900 proceeds to 3934.

At 3934, method 3900 removes the cylinder with one or more valves thatdid not activate from a list of cylinders that may be activated. Thus,method 3900 inhibits cylinder activation for the cylinder with valvesthat did not activate when the valves were commanded to be activated.Combustion is inhibited in cylinders removed from the list of cylindersthat may be activated. Method 3900 proceeds to 3936.

At 3936, method 3900 provides a requested engine torque up to thecapacity of cylinders in the list of cylinders that may be activated.The actual total number of cylinders that are active may be increased inresponse to the engine torque request or decreased in response to theengine torque request. As a result, a significant amount of enginetorque may be provided even if poppet valves of one or more cylindersbecome degraded. Method 3900 proceeds to exit.

At 3940, method 3900 provides a desired amount of engine torque viaactive cylinders. The desired amount of engine torque may be based on adriver demand torque, and the driver demand torque may be based on aposition of an accelerator pedal and vehicle speed. The desired amountof torque from the active cylinders is provided by controlling air flowand fuel flow to the active cylinders. Method 3900 proceeds to exit.

Referring now to FIG. 40, a sequence for operating an engine accordingto the method of FIG. 39 is shown. The vertical lines at timeT4000-T4005 represent times of interest in the sequence. FIG. 40 showsfive plots and the plots are time aligned and occur at the same time.The SS along the time line of each plot indicates a break in thesequence. The time between the break may be long or short. The sequenceof FIG. 40 represents a sequence for operating a four cylinder enginewith a firing order of 1-3-4-2.

The first plot from the top of FIG. 40 is a plot of cylinderdeactivation request (e.g., a request to cease combustion in one or morecylinders) versus time. The vertical axis represents the cylinderdeactivation request and cylinder deactivation is requested when thetrace it at a level near the vertical axis arrow. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The second plot from the top of FIG. 40 is a plot of cylinder number twovalve operating state versus time. Cylinder valves in cylinder numbertwo are active when the trace is at a higher level near the verticalaxis arrow. Cylinder valves in cylinder number two are inactive when thetrace is at a lower level near the horizontal axis. The horizontal axisrepresents time and time increases from the left side of the figure tothe right side of the figure.

The third plot from the top of FIG. 40 is a plot of cylinder numberthree valve operating state versus time. Cylinder valves in cylindernumber three are active when the trace is at a higher level near thevertical axis arrow. Cylinder valves in cylinder number three areinactive when the trace is at a lower level near the horizontal axis.The horizontal axis represents time and time increases from the leftside of the figure to the right side of the figure.

The fourth plot from the top of FIG. 40 is a plot of an actual totalnumber of requested active cylinders versus time. The vertical axisrepresents the actual total number of requested active cylinders and theactual total number of requested active cylinders is posted along thevertical axis. The horizontal axis represents time and time increasesfrom the left side of the figure to the right side of the figure.

The fifth plot from the top of FIG. 40 is a plot of requested enginetorque versus time. The vertical axis represents requested engine torqueand the value of the requested engine torque increases in the directionof the vertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure.

At time T4000, cylinders are not requested deactivated as indicated bythe cylinder deactivation request being at a lower level. Valves ofcylinder number two and three are active. The valves of cylinder numberstwo and three are active based on the number of requested active (e.g.,combusting air and fuel) cylinders being four. The requested enginetorque is at a higher level.

At time 4001, the requested engine torque decreases. The requestedengine torque may decrease in response to a decrease in driver demandtorque. The number of requested engine cylinders is decreased from fourto three in response to the requested engine torque decrease. Further,the cylinder deactivation request is asserted in response to thedecrease in requested engine torque. Cylinder number two is requesteddeactivated and cylinder poppet valves of cylinder number two arecommanded closed. However, the valves of cylinder number two remainactive as indicated by the cylinder number two valve state. Because thepoppet valves of cylinder number two remained active (e.g., opening andclosing as the engine rotates through an engine cycle), cylinder numbertwo is commanded reactivated as indicated by the number of requestedactive cylinders transitioning back to four. Shortly thereafter,cylinder number three is commanded deactivated in response to the numberof active cylinders changing back to three. The poppet valves ofcylinder number three become inactive (e.g., are held closed during theengine cycle) and the requested number of active cylinders remainsconstant at a value of three.

At time T4002, the requested engine torque increases and the number ofrequested active cylinders is increased back to four. Cylinder numberthree is reactivated and the valves of cylinder number three areactivated as indicated by the cylinder number three valve state.Cylinder number two remains active and the cylinder deactivation requestis not asserted in response to the number of requested active cylinders.

At time T4003, the cylinder deactivation request is asserted in responseto the number of requested active cylinders being two. The valves ofcylinder number two and cylinder number three are inactive. Therequested engine torque is at a low level that allows the engine toprovide the requested torque will less than its full complement ofcylinders being active.

At time 4004, the engine torque request increases in response to anincrease in driver demand torque (not shown). The number of requestedactive cylinders increases to a value of four in response to theincreased requested torque. Valves of cylinder number three reactivate,but valves of cylinder number two do not reactivate in response to thenumber of requested active cylinders. Shortly after time T4004, thenumber of requested active cylinders transitions to a value of three andcylinder number two is commanded deactivated (e.g., cease delivery offuel and hold poppet valves closed during an engine cycle). Further, thecylinder deactivation request is asserted again for cylinder number two.The engine provides as much of the requested torque as the torquecapacity of the three active cylinders permits.

At time 4005, the requested engine torque is decreased in response to adecrease in driver demand torque. The number of requested activecylinders is decreased from three to two in response to the decrease inrequested engine torque. The valves of cylinder number three aredeactivated and cylinder numbers two and three are deactivated inresponse to the number of requested active cylinders. The cylinderdeactivation request is also remains asserted.

In this way, the number of requested active engine cylinders may beadjusted responsive to valves that may not be deactivated when they arerequested deactivated. Further, the number of requested active enginecylinders may be adjusted responsive to valves that may be deactivatewhen they are requested activated.

Referring now to FIG. 41, a method for sampling oxygen sensors of anengine with cylinder deactivation is shown. The method of FIG. 41 may beincluded in the system described in FIGS. 1A-6C. The method of FIG. 41may be included as executable instructions stored in non-transitorymemory. The method of FIG. 41 may perform in cooperation with systemhardware and other methods described herein to transform an operatingstate of an engine or its components.

At 4102, method 4100 judges if one or more cylinders of the engine aredeactivated. Method 4100 may evaluate a value of a variable stored inmemory to determine if one or more engine cylinders are deactivated. Ifmethod 4100 judges that one or more engine cylinders are deactivated,the answer is yes and method 4100 proceeds to 4104. Otherwise, theanswer is no and method 4100 proceeds to 4120.

At 4120, method 4100 samples an oxygen sensor of a cylinder bank twiceper exhaust stroke of each cylinder on the cylinder bank. Thus, if theengine is a four cylinder engine with a single bank of cylinders, method4100 samples the exhaust sensor eight times in two engine revolutions.The samples are then averaged to provide an air-fuel ratio estimate forthe engine. Additionally, cylinder specific air-fuel ratios may beestimated via averaging the two samples taken during a cylinder'sexhaust stroke to determine the cylinder's air-fuel ratio. Method 4100proceeds to 4108.

At 4108, method 4100 adjusts fuel supplied to engine cylinders based onthe oxygen sensor samples. If the oxygen sensor indicates a leanerair-fuel ratio than is desired, additional fuel may be injected to theengine. If the oxygen sensor indicates a richer air-fuel ratio than isdesired, less fuel may be injected to the engine. Method 4100 proceedsto exit.

At 4104, method 4100 determines which engine cylinders are deactivated.In one example, method 4100 evaluates values stored in memory thatindicate active and deactivated cylinders. Method 4100 determines whichcylinders are deactivated and proceeds to 4106.

At 4106, method 4100 samples an oxygen sensor of a cylinder bank twiceper exhaust stroke of each cylinder on the cylinder bank, except forexhaust strokes of deactivated cylinders which are not sampled.Alternatively, oxygen samples taken during exhaust strokes ofdeactivated cylinders may be discarded. The samples are then averaged todetermine an average engine air-fuel ratio. Method 4100 proceeds to4108.

By not sampling oxygen sensors during exhaust strokes of deactivatedcylinders, it may be possible to reduce air-fuel ratio bias that may beinduced on an engine air-fuel estimate. In particular, if one cylinderair-fuel mixture is leaner or richer than other cylinders and itsexhaust gases are expelled near an exhaust stroke of a deactivatedcylinder, bias to the engine air-fuel ratio may be reduced by notsampling output from the cylinder that is leaner or richer twice duringan engine cycle.

Referring now to FIG. 42, a method for sampling cam sensors of an enginewith cylinder deactivation is shown. The method of FIG. 42 may beincluded in the system described in FIGS. 1A-6C. The method of FIG. 42may be included as executable instructions stored in non-transitorymemory. The method of FIG. 42 may perform in cooperation with systemhardware and other methods described herein to transform an operatingstate of an engine or its components.

At 4202, method 4200 judges if one or more cylinders of the engine aredeactivated. Method 4200 may evaluate a value of a variable stored inmemory to determine if one or more engine cylinders are deactivated. Ifmethod 4200 judges that one or more cylinders are deactivated, theanswer is yes and method 4200 proceeds to 4204. Otherwise, the answer isno and method 4200 proceeds to 4220.

At 4220, method 4200 samples an intake cam sensor twice per intakestroke of each cylinder on a cylinder bank that includes an intake cammonitored by the intake cam sensor. Likewise, method 4200 samples anexhaust cam sensor twice per exhaust stroke of each cylinder on acylinder bank that includes an exhaust cam monitored by the exhaust camsensor. Thus, if the engine is a four cylinder engine with a singleintake cam, method 4200 samples the cam sensor eight times in two enginerevolutions. Cam position and speed may be determined for each camsensor sample taken. Method 4200 proceeds to 4208.

At 4208, method 4200 adjusts a cam phase actuator command to adjust camposition based on the cam sensor samples. If the cam sensor indicatescam position is not at its desired position and/or if the cam is movingslower or faster than is desired, the cam phase command is adjusted toreduce the error between the actual cam position and the desired camposition. Method 4200 proceeds to exit.

At 4204, method 4200 determines which engine cylinders are deactivated.In one example, method 4200 evaluates values stored in memory thatindicate active and deactivated cylinders. Method 4200 determines whichcylinders are deactivated and proceeds to 4206.

At 4206, method 4200 samples a cam sensor of a cylinder bank twice perintake stroke for an intake cam or twice for each exhaust stroke for anexhaust cam, except for exhaust strokes of deactivated cylinders whichare not sampled. Alternatively, cam sensor samples taken during intakeor exhaust strokes of deactivated cylinders may be discarded. Thesamples are then processed to determine cam position and speed.Additionally, cam samples may be averaged to reduce cam signal noise.Method 4200 proceeds to 4208.

By not sampling cam sensors during intake or exhaust strokes ofdeactivated cylinders, it may be possible to reduce cam position biasthat may be induced on engine cam position. The rate a cam phaseactuator moves may be affected by whether or not a cylinder isdeactivated. Therefore, it may be desirable to eliminate cam samplestaken when valve springs of deactivated cylinders are not assisting cammovement relative to crankshaft position.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, atleast a portion of the described actions, operations and/or functionsmay graphically represent code to be programmed into non-transitorymemory of the computer readable storage medium in the control system.The control actions may also transform the operating state of one ormore sensors or actuators in the physical world when the describedactions are carried out by executing the instructions in a systemincluding the various engine hardware components in combination with oneor more controllers.

This concludes the description. The reading of it by those skilled inthe art would bring to mind many alterations and modifications withoutdeparting from the spirit and the scope of the description. For example,I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas,gasoline, diesel, or alternative fuel configurations could use thepresent description to advantage.

The invention claimed is:
 1. A method for operating an engine,comprising: generating a first knock reference value from a knock sensoroutput provided to a controller during a first cycle of a cylinder whena cylinder's valves are active and combustion occurs in the cylinder;generating a second knock reference value from the knock sensor outputprovided to the controller during a second cycle of the cylinder whenthe cylinder's valves are not active and combustion does not occur inthe cylinder; judging a presence or absence of knock based on the firstknock reference value during a first condition; judging the presence orabsence of knock based on the second knock reference value during asecond condition; and adjusting engine spark timing via the controllerbased on the presence or absence of knock.
 2. The method of claim 1,further comprising generating a third knock reference value from theknock sensor output provided to the controller during a third cycle ofthe cylinder when at least one of the cylinder's valves are active andcombustion does not occur in the cylinder, and judging the presence orabsence of knock based on the third knock reference value during a thirdcondition.
 3. The method of claim 2, where the first condition iscombustion in all cylinders of the engine.
 4. The method of claim 3,where the second condition is the first knock reference value beinggreater than a threshold.
 5. The method of claim 2, where the thirdcondition is the first knock reference value being greater than athreshold.
 6. The method of claim 2, further comprising integrating theknock sensor output and dividing the integrated knock sensor output bythe first knock reference value, the second knock reference value, orthe third knock reference value.
 7. The method of claim 2, furthercomprising integrating the knock sensor output and dividing theintegrated knock sensor output by the first knock reference value, thesecond knock reference value, or the third knock reference value basedon mapped expected knock reference values.
 8. The method of claim 7,where the presence of knock is determined via comparing a knockintensity to a threshold value.